CHIPSETS
A chipset or "PCIset" is a group of microcircuits that orchestrate the flow of data to and from key components of a PC. This includes the CPU itself, the main memory, the secondary cache and any devices situated on the ISA and PCI buses. The chipset also controls data flow to and from hard disks, and other devices connected to the IDE channels. While new microprocessor technologies and speed improvements tend to receive all the attention, chipset innovations are, in fact, equally important.
Although there have always been other chipset manufacturers - such as SIS, VIA and Opti - for many years Intel's "Triton" chipsets were by far the most popular. Indeed, the introduction of the Intel Triton chipset caused something of a revolution in the motherboard market, with just about every manufacturer using it in preference to anything else. Much of this was down to the ability of the Triton to get the best out of both the Pentium processor and the PCI bus, together with its built-in master EIDE support, enhanced ISA bridge and ability to handle new memory technologies like EDO and SDRAM. However, the new PCI chipsets" potential performance improvements will only be realised when used in conjunction with BIOSes capable of taking full advantage of the new technologies on offer.
During the late 1990s things became far more competitive, with Acer Laboratories (ALI), SIS and VIA Technologies all developing chipsets designed to operate with Intel, AMD and Cyrix processors. 1998 was a particularly important year in chipset development, with what had become an unacceptable bottleneck - the PC's 66MHz system bus - to finally being overcome. Interestingly, it was not Intel but rival chipmakers that made the first move, pushing Socket 7 chipsets to 100MHz. Intel responded with its 440BX, one of many chipsets to use the ubiquitous Northbridge/Southbridge architecture. It was not long before Intel's hold on the chipset market loosened further still, and again, the company had no-one but itself to blame. In 1999, its single-minded commitment to Direct Rambus DRAM (DRDRAM) left it in the embarrassing position of not having a chipset that supported the 133MHz system bus speed its latest range of processors were capable of. This was another situation it's rivals were able to exploit, and in so doing gain market share.
The following charts the evolution of Intel chipsets over the years, from the time of it's first Triton chipset. During this time there have also been a number of special chipsets optimised for the Pentium Pro or designed for use with notebook PCs.
Triton 430FX
Introduced in early 1995, the 82430FX - to give it its full name - was Intel's first Triton chipset and conformed to the PCI 2.0 specification. It introduced support for EDO memory configurations of up to 128MB and for pipelined burst cache and synchronous cache technologies. However, it did not support a number of emerging technologies such as SDRAM and USB and was superseded in 1996 - little more than a year after its launch - by a pair of higher performance chipsets.
Triton 430VX
The Triton 430VX chipset conforms to the PCI 2.1 specification, and is designed to support Intel's Universal Serial Bus (USB) and Concurrent PCI standards. With the earlier 430FX, a bus master (on the ISA or PCI bus), such as a network card or disk controller, would lock the PCI bus whenever it transferred data in order to have a clear path to memory. This interrupted other processes, and was inefficient because the bus master would never make full use of the 100 MBps bandwidth of the PCI bus. With Concurrent PCI, the chipset can wrest control of the PCI bus from an idle bus master to give other processes access on a timeshare basis. Theoretically, this should allow for data transfer rates of up to 100 MBps, 15% more than the 430FX chipset, and smooth intensive PCI tasks such as video playback when bus masters are present.
The 430VX chipset was aimed fairly and squarely at the consumer market. It was intended to speed up multimedia and office applications, and it was optimised for 16-bit. Furthermore, it was designed to work with SDRAM, a special type of memory that's optimised for intensive multimedia processing. Although the performance gains are slight for this type of RAM over EDO RAM, the advantage is that it can operate efficiently from a single Dual In-line Memory Module (DIMM) and does not need to be paired.
The 430VX provided improved EDO memory timings which was supposed to allow cacheless systems to be built without compromising performance, at least compared to a PC with asynchronous cache. In practice, though, most manufacturers continued to provide at least some secondary cache, with most using synchronous cache to maximise performance.
Triton 430HX
The Triton 430HX chipset is geared towards business machines and was developed with networking, video conferencing and MPEG video playback in mind. It supports multiple processors, has been optimised for 32-bit operation and to work with large memory arrays (up to 512MB) and provides error control (ECC) facilities on the fly when 32-bit parity SIMMs are used. The 430HX does not support SDRAM.
The biggest difference between the HX and VX chipsets is the packaging. Where the VX consists of four separate chips, all built using the traditional plastic quad flat packaging, the HX chipset comprises just two chips, the 82439HX System Controller (SC), which manages the host and PCI buses, and the 82371SB PIIX3 for the ISA bus and all the ports.
The SC comes in a new ball grid array (BGA) packaging which reduces overall chip size and makes it easier to incorporate onto motherboard designs. It exerts the greatest influence on the machine's CPU performance, as it manages communications between the CPU and memory. The CPU has to be fed data from the secondary cache as quickly as possible, and if the necessary data isn"t already in the cache, the SC fetches it from main memory and loads it into the cache. The SC also ensures that data written into cache by the CPU is "flushed" back into main memory.
The PIIX3 chip manages the many processes involved in getting data into and out of RAM from the other devices in the PC. It provides two EIDE channels, both of which can accept two drives. IDE drives contain most of the controlling circuitry built into the hard disk itself, so the PIIX is mainly responsible for shifting data from the drives into RAM and back as quickly as possible. It also provides two 115,200bit/s buffered serial ports, an error correcting Enhanced Parallel Port, a PS/2 mouse port and a keyboard controller. The PIIX also supports additional connections that many motherboards have yet to adopt as the norm, such as a Universal Serial Bus connector and an infrared port.
Triton 430TX
The Triton 430TX includes all the features found on the earlier chipsets, including Concurrent PCI, USB support, aggressive EDO RAM timings and SDRAM support and is optimised for MMX processors and is designed to be used in both desktop and mobile computers.
The Triton 430TX also continues the high-integration two-chip BGA packaging first seen with the 430HX chipset, comprising the 82439TX System Controller (MTXC) and the 82371AB PCI ISA IDE Xcelerator (PIIX4). The former integrates the cache and main memory DRAM control functions and provides bus control to transfers between the CPU, cache, main memory, and the PCI Bus. The latter is a multi-function PCI device implementing a PCI-to-ISA bridge function, a PCI IDE function, a Universal Serial Bus host/hub function, and an Enhanced Power Management function.
The diagram below provides an overview of the overall architecture and shows the division of functionality between the System Controller and the Peripheral Bus Controller components - which are often referred to as "Northbridge" and "Southbridge" chipsets respectively.
The TX incorporates the Dynamic Power Management Architecture (DPMA) which reduces overall system power consumption and offers intelligent power-saving features like suspend to RAM and suspend to disk. The TX chipset also supports the new Ultra DMA disk protocol which enables a data throughput of 33 MBps from the hard disk drive to enhance performance in the most demanding applications.
440LX
The 440LX (by this time Intel had dropped the term "Triton") was the successor to the Pentium Pro 440FX chipset and was developed by Intel to consolidate on the critical success of the Pentium II processor launched a few months earlier. The most important feature of the 440LX is support for the Accelerated Graphics Port (AGP), a new, fast, dedicated bus designed to eliminate bottlenecks between the CPU, graphics controller and system memory, which will aid fast, high-quality 3D graphics.
Other improvements with the LX are more like housekeeping, bringing the Pentium II chipset up to the feature set of the 430TX by providing support for SDRAM and Ultra DMA IDE channels. The chipset includes the Advanced Configuration and Power Interface (ACPI), allowing quick power down and up, remote start-up over a LAN for remote network management, plus temperature and fan speed sensors. The chipset also has better integration with the capabilities of the Pentium II, such as support for dynamic execution and processor pipelining.
440EX
The 440EX AGPset, based on the core technology of the 440LX AGPset, is designed for use with the Celeron family of processors. It is ACPI-compliant and extends support for a number of advanced features such as AGP, UltraDMA/33, USB and 66MHz SDRAM, to the "Basic PC" market segment.
440BX
The PC's system bus had been a bottleneck for too long. Manufacturers of alternative motherboard chipsets had made the first move, pushing Socket 7 chipsets beyond Intel's 66MHz. Intel's response came in April 1998, with the release of its 440BX chipset, which represented a major step in the Pentium II architecture. The principal advantage of the 440BX chipset is support for a 100MHz system bus and 100MHz SDRAM. The former 66MHz bus speed is supported, allowing the BX chipset to be used with older (233MHz-333MHz) Pentium IIs.
The 440BX chipset features Intel's Quad Port Acceleration (QPA) to improve bandwidth between the Pentium II processor, the Accelerated Graphics Port, 100-MHz SDRAM and the PCI bus. QPA combines enhanced bus arbitration, deeper buffers, open-page memory architecture and ECC memory control to improve system performance. Other features include support for dual processors, 2x AGP, and the Advanced Configuration Interface (ACPI).
440ZX
The 440ZX is designed for lower cost form factors without sacrificing the performance expected from an AGPset, enabling 100MHz performance in form factors like microATX. With footprint compatibility with the 440BX, the 440ZX is intended to allow OEMs to leverage BX design and validation investment to produce new systems to meet entry level market segment needs.
440GX
Released at the same time as the Pentium II Xeon processor in mid-1998, the 440GX chipset was an evolution of the 440BX AGPset intended for use with Xeon-based workstations and servers. Built around the core architecture of its 440BX predecessor, the 440GX includes support for both Slot 1 and Slot 2 implementations, a 2x AGP expansion slot, dual CPUs and a maximum of 2GB of memory.
Importantly, the chipset supports full speed backside bus operation, enabling the Pentium II Xeon's Level 2 cache to run at the same speed as the core of the CPU.
810 AGPset
Formerly codenamed "Whitney", the 810 AGPset finally reached the market in the summer of 1999. It is a three-chip solution comprising the 82810 Graphics Memory Controller Hub (GMCH), 82801 I/O Controller Hub (ICH) and 82802 Firmware Hub (FWH) for storing the system and video BIOS. A break from tradition is that these components don't communicate with each other over the PCI bus. Instead, they use a dedicated 8-bit 266 MBps proprietary bus, thereby taking load off the PCI subsystem. The SDRAM memory interface is also unusual in that it runs at 100MHz irrespective of the system bus speed. There's no ISA support, but it could be implemented if a vendor added an extra bridge chip.
At the time of its launch, there were two versions of the 810 - the 82810 and 81810-DC100. The former is 66MHz part with no graphics memory, while the latter is a 100MHz-capable chip with support for 4MB of on-board graphics memory. The Direct AGP graphics architecture uses 11MB of system memory for frame buffer, textures and Z-buffer if no display cache is implemented. This drops to 7MB if the display cache is implemented. The whole configuration is known as Direct Video Memory technology. Also incorporated in the chipset is an AC-97 CODEC, which allows software modem and audio functionality. Vendors can link this to an Audio Modem Riser (AMR) slot to facilitate future plug-in audio or modem upgrades.
In the autumn of 1999 a subsequent version of the chipset - the 810E - extended support processors with a 133 MHz system bus. The Intel 810E chipset features a unique internal gear arbitration, allowing it to run seamlessly with 66 MHz, 100 MHz and 133 MHz processor busses.
As the cost of processors come down, the marginal costs of the motherboard, graphics and sound subsystems becomes an increasingly important factor in vendors' efforts to hit ever-lower price points. However, high levels of integration can be a double-edged sword: it reduces vendors' bill-of-materials (BOM) costs, but also limits their capability for product differentiation. Many manufacturers defer their decisions on graphics and sound options to late in the production cycle in order to maintain a competitive marketing advantage. Given that other highly integrated solutions - such as Cyrix's Media GX - haven't fared particularly well in the past, the 810 AGPset represents a bold move on Intel's part and one that signals the company's determination to capture a greater share of the "value PC" market which had been effectively ceded to AMD and Cyrix over the prior couple of years.
820 chipset
Originally scheduled to be available concurrently with the Pentium III processor in the spring of 1999, Intel's much delayed 820 chipset was finally launched in November that year. Those delays - which had left Intel in the position not having a chipset that supported the 133MHz system bus speed their latest range of processors were capable of - were largely due to delays in the production of Direct Rambus DRAM (DRDRAM), a key component in Intel's 133MHz platform strategy.
Direct RDRAM memory provides a memory bandwidth capable of delivering 1.6 GBps of maximum theoretical memory bandwidth - twice the peak memory bandwidth of 100MHz SDRAM systems. Additionally, the 820's support for AGP 4x technology allows graphics controllers to access main memory at more than 1 GBps - twice that of previous AGP platforms. The net result is the significantly improved graphics and multimedia handling performance expected to be necessary to accommodate future advances in both software and hardware technology.
The 820 chipset employs the Accelerated Hub Architecture that is offered in all Intel 800 series chipsets - the first chipset architecture to move away from the traditional Northbridge /Southbridge design. It supports a bandwidth of 266 MBps and, with it's optimised arbitration rules which allow more functions to run concurrently, delivers significantly improved audio and video handling. The chipset's three primary components are:
• Memory Controller Hub
• I/O Controller Hub, and
• Firmware Hub.
The Memory Controller Hub provides a high-performance interface for the CPU, memory and AGP and supports up to 1GB of memory via a single channel of RDRAM using 64-, 128- and 256-Mbit technology. With an internal bus running at 1.6 GBps and an advanced buffering and queuing structure, the Memory Hub Controller balances system resources and enables concurrent processing in either single or dual processor configurations.
The I/O Controller Hub forms a direct connection from the PC's I/O devices to the main memory. This results in increased bandwidth and significantly reduced arbitration overhead, creating a faster path to main memory. To capitalise further on this faster path to main memory, the 820 chipset features an integrated AC97 controller in addition to an ATA66 drive controller, dual USB ports and PCI add-in cards.
The Firmware Hub stores system and video BIOS and includes a first for the PC platform - a hardware-based random number generator. The Intel RNG provides truly random numbers through the use of thermal noise - thereby enabling stronger encryption, digital signing and security protocols. This is expected to be of particular benefit to the emerging class of e-commerce applications.
The i820 hadn't long been on the market before Intel - recognising that the price of RDRAM was likely to remain high for sometime - designed and released an add-on chip, the 82805 Memory Translator Hub (MTH), which, when implemented on the motherboard, allowed the use of PC100 SDRAM. Sitting between the i820's Memory Controller Hub (MCH) and the RDRAM memory slots, the MTH chip translates the Rambus memory protocol that's used by RDRAM into the parallel protocol required by SDRAM, thereby allowing the i820 to use this much more price attractive memory.
Within a few months, a bug in the MTH component came to light. This was serious enough to cause Intel to recall all MTH-equipped i820-motherboards. Since it wasn't possible to replace the defective chip Intel took the extraordinary step of giving every owner of an MTH-equipped i820 motherboard a replacement non-MTH motherboard as well as RDRAM to replace the SDRAM that was used before!
815 chipset
The various problems that had so delayed the introduction of Direct Rambus DRAM (DRDRAM), finally resulted in Intel doing what it had been so reluctant to do for so long - release a chipset supporting PC133 SDRAM. In fact, in mid-2000, it announced two such chipsets - formerly codenamed "Solano" - the 815 Chipset and the 815E Chipset.
Both chipsets use Intel's Graphics and Memory Controller Hub (GMCH). This supports both PC133 and PC100 SDRAM and provides onboard graphics, with a 230MHz RAMDAC and limited 3D acceleration. This gives system integrators the option of using the on-board graphics - and system memory - for lower cost systems or upgrading via an external graphics card for either AGP 4x or AGP 2x graphics capabilities.
Additionally, and like the 820E Chipset before it, the 815E features a new I/O Controller Hub (ICH2) for greater system performance and flexibility. This provides an additional USB controller, a Local Area Network (LAN) Connect Interface, dual Ultra ATA /100 controllers and up to six-channel audio capabilities. Integrating a Fast Ethernet controller directly into the chipsets makes it easier for computer manufacturers and system integrators to implement cost-effective network connections into PCs. The ICH2's enhanced AC97 interface supports full surround-sound for Dolby Digital audio found on DVD and simultaneously supports a soft modem connection.
850 chipset
Designed in tandem with the Pentium 4 processor, Intel's 850 Chipset represents the next step in the evolution of the Intel Hub Architecture, the successor to the previous northbridge /southbridge technology first seen on the 810 Chipset. Comprising the 82850 Memory Controller Hub (MCH) and 82801BA I/O Controller Hub (ICH2), the new chipset's principal features are:
• a 400MHz system bus
• dual RDRAM memory channels, operating in lock step to deliver 3.2 GBps of memory bandwidth to the processor
• support for 1.5V AGP4x technology, allowing graphics controllers to access main memory at over 1 GBps - twice the speed of previous AGP platforms
• two USB controllers, doubling the bandwidth available for USB peripherals to 24 MBps over four ports
• dual Ultra ATA/100 controllers support the fastest IDE interface for transfers to storage devices.
To ensure maximum performance, the system bus is balanced with the dual RDRAM channels at 3.2 GBps, providing 3x the bandwidth of platforms based on Intel III processors and allowing better concurrency for media-rich applications and multitasking.
In the autumn of 2002, some 18 months after the i850 was first introduced, the i850E variant was released, extending the capabilities of the chipset to support Hyper-Threading, a 533MHz system bus and PC1066 memory, for Pentium 4 class processors.
i845 chipset
The fact that system builders were obliged to use expensive DRDRAM - by virtue of the absence of any Pentium 4 chipsets supporting conventional SDRAM - had been an issue ever since the Pentium 4's launch at the end of 2000. The situation changed during the course of 2001, with chipmakers SiS and VIA both releasing Pentium 4 chipsets with DDR SDRAM support. Although this was a move of which Intel disapproved, it did have the effect of boosting the appeal of the Pentium 4, whose sales hitherto had been disappointing.
In the summer of 2001 Intel eventually gave in to market pressures and released their 845 chipset - previously codenamed "Brookdale" - supporting Pentium 4 systems' use of PC133 SDRAM. Whilst the combination of i845 and PC133 SDRAM meant lower prices - given that the speed of the memory bus was about three times slower than that of the Pentium 4 system bus - it also meant significantly poorer performance than that of an i850/DRDRAM based system. The reason the i845 didn't support faster DDR SDRAM at this time was apparently because they were prevented from allowing this until the start of the following year by the terms of a contract they'd entered into with Rambus, the inventors of DRDRAM.
Sure enough, at the beginning of 2002 re-released of the i845 chipset. The new version - sometimes being referred to as i845D - differs from its predecessor only in respect of its memory controller, which now supports PC1600 and PC2100 SDRAM - sometimes referred to as DDR200 and DDR266 respectively - in addition to PC133 SDRAM. It had reportedly been Intel's original intention for the i845 chipset to support only DDR200 SDRAM - capable of providing a maximum bandwidth of 1600MBps. However, the boom in the use of DDR SDRAM - and the consequent dramatic fall in prices - caused a rethink and the subsequent decision to extend support to DDR266 (maximum bandwidth 2100MBps). The fact that the company was prepared to make this decision even though it was bound to adversely impact the market share of its i850 chipset appears to indicate that the company's apparent infatuation with DRDRAM is well and truly over.
The 400MHz system bus of the i845 solution enables up to 3.2GBps of memory bandwidth to Pentium 4 processor. Compare this with the up to 1 GBps of data transfer possible from PC133 SDRAM and it is clear why faster DDR SDRAM makes such a difference to overall system performance. Its 1.5V 4x AGP interface with provides over 1 GBps of graphics bandwidth. Other features of the i845 chipset include an 4x AGP interface, 133MBps to the PCI, support for four USB ports, six-channel audio, a generally unused LAN connect interface, dual ATA-100 controllers and CNR support.
The i845 is Intel's first chipset to use a Flip Chip BGA packaging for the chip itself. This improves heat conductivity between the Memory & Controller Hub (MCH) and its heatsink which is required for proper operation. It is also the first MCH built using a 0.18-micron process; earlier versions have been 0.25-micron. The smaller die allows another first - the incorporation of a Level 3-like write cache, significantly increasing the speed at which the CPU is able to write data. It is expected that the transition to 0.13-micron MCH/Northbridges will enable this idea to be further developed, to the point where chipsets include much larger, genuine Level 3 caches on the MCH itself. The i845 further capitalises on the performance advantage realised by its high-speed write cache by the provision of deep data buffers. These play an important role in assisting the CPU and write cache to sustain its high data throughput levels.
A number of newer versions of the i845 chipset were subsequently released, all supporting the USB 2.0 interface (which increases bandwidth up to 40 times over the previous USB 1.1 standard):
• The i845G chipset, incorporating a new generation of integrated graphics - dubbed Intel Extreme Graphics - and targeted at the high-volume business and consumer desktop market segments.
• The i845E chipset, which works with discrete graphics components
• The i845GL chipset, designed for Celeron processor-based PCs.
i845GE chipset
The i845GE chipset was designed and optimised to support Hyper-Threading, Intel's innovative technology that achieves significant performance gains by allowing a single processor to be treated as two logical processors. Whilst not the first i845 chipset to support HT technology, it was the first in which that support was actually implemented, being launched at the same time as the first Intel's first HT-enabled desktop CPU, the 3.06GHz Pentium 4 unveiled in late 2002.
As well as supporting a faster, 266MHz version of Intel's Extreme Graphics core, the i845GE also supports a system bus speed of either 400 or 533MHz, up to DDR333 main memory and offers maximum display (digital CRT or TV) flexibility through an AGP4x connector.
The i845PE and i845GV chipsets are lower-spec variants of the i845GE, the former having no integrated graphics and the latter limiting both the Intel Extreme Graphics core and main memory support to DDR266 SDRAM.
Intel E7205 chipset
At the end of 2002, Intel announced the launch of a dozen Intel Xeon processor family products, including new processors, chipsets and platforms for Intel-based servers and workstations. Amongst these was one single-processor chipset, the E7205, formerly codenamed Granite Bay.
For some time the most viable way of balancing the bandwidth between the Pentium 4 CPU and its memory subsystem had been to couple the i850E chipset with dual-channel RDRAM. However, given the price and availability issues surrounding high-density RDRAM modules, this was a far from ideal solution. Despite - as it's server/workstation class chipset nomenclature implies - not originally being intended for desktop use, the E7205 chipset was to provide an answer to this dilemma. With a specification which includes support for:
• Dual Channel DDR266 memory bus (4.2GBps memory bandwidth)
• 400/533MHz FSB support (3.2GBps - 4.2GBps FSB bandwidth)
• AGP 8x
• USB 2.0, and
• integrated LAN.
it didn't take long for the motherboard manufacturers to produce boards based on the new chipset.
The E7205's memory controller is fully synchronous, meaning that the memory in E7205-based motherboards is clocked at the rate equal to the FSB frequency. Consequently, only DDR200 SDRAM may be used with CPUs supporting a 400MHz FSB and only DDR266 SDRAM with processors supporting a 533MHz FSB. The E7205 does not support DDR333 SDRAM.
With the Pentium 4 family destined to make the transition to a 800MHz Quad Pumped Bus - at which time the CPU's bus bandwidth will increase to 6.4GBps - it appears reasonable to assume that the likely way for memory subsystems to have comparable bandwidth will be the continued use of dual-channel DDR SDRAM. To that extent, the E7205 can be viewed as a prototype of the Canterwood and Springdale chipsets slated to appear in 2003.
i875P chipset
Originally, Intel had planned to introduce a 800MHz FSB in the context of the Prescott, the upcoming 90nm Pentium 4 core. However, in the event this was brought forward to the spring of 2003. The rationale was to extend the Pentium 4's performance curve within the confines of their current 0.13-micron process, without having to increase clock speeds to unsustainable levels. The transition from 533MHz to 800MHz FSB was aided and abetted by an associated new chipset platform, the 875P chipset, formerly codenamed Canterwood.
A 64-bit 800MHz FSB provides 6.4GBps of bandwidth between the Memory Controller Hub (or Northbridge) and the CPU. In a move that appears to further reduce the strategic importance of DRDRAM in Intel's product planning, and that had been signalled by the earlier E7205 chipset, the memory subsystem the 875P uses to balance bandwidth between the Memory Controller Hub (MCH) and memory banks is dual channel DDR SDRAM, all of the DDR400, DDR333 and DD266 variants.
Currently, there are two different strategies being employed in dual-channel memory controllers, one in which where each memory bank has its own memory channel and an arbiter distributes the load between them and the other to actually create a wider memory channel, thereby "doubling up" on standard DDR's 64-bit data paths. The i875P employs the latter technique, with each pair of installed DIMMs acting as a 128-bit memory module, able to transfer twice as much data as a single-channel solution, without the need for an arbiter.
As a consequence, dual channel operation is dependent on a number of conditions being met, Intel specifying that motherboards should default to single-channel mode in the event of any of these being violated:
• DIMMs must be installed in pairs
• Both DIMMs must use the same density memory chips
• Both DIMMs must use the same DRAM bus width
• Both DIMMs must be either single-sided or dual-sided.
The 875P chipset also introduces two significant platform innovations:
• Intel Performance Acceleration Technology (PAT), and
• Communications Streaming Architecture (CSA).
PAT optimises memory access between the processor and system memory for platforms configured with both the new 800Mhz FSB and Dual-Channel DDR400 memory. CSA is a new communications architecture that creates a dedicated link from the Memory Controller Hub (MCH) to the network interface, thereby offloading network traffic from the PCI bus. Used in conjunction with the new Intel PRO/1000 CT Desktop Connection gigabit Ethernet controller, it is claimed that CSA doubles the networking bandwidth possible with traditional PCI bus-based solutions.
Additionally, the 875P chipset includes a high-performance AGP 8x graphics interface, integrated Hi-Speed USB 2.0, optional ECC is supported for users that demand memory data reliability and integrity and dual independent DMA audio engines, enabling a user to make a PC phone call whilst at the same time playing digital music streams. The chipset is also Intel's first to offer native Serial ATA (SATA), a special version designated by the "-R" suffix adding RAID - albeit only RAID 0 (data striping) - support.
i865 chipset
If the i875 chipset can be viewed as the logical successor to i850E, then it's mainstream variant, the i865 chipset - formerly codenamed Springdale - can be viewed as the logical successor to the i845 series of chipsets. Not only do the i875/i865 chipsets represent a huge technological leap compared to their predecessors, but the performance gap between the pair of recent chipsets is significantly less than it was between the i850E and i845 family.
There is a clear trend in PC hardware towards parallel processes, epitomised by Intel's Hyper-Threading technology. However, there are other examples of where performing several tasks at the same time is preferable to carrying out a single task quickly. Hence the increasing popularity of small RAID arrays and now the trend towards dual-channel memory subsystems.
Currently, there are two different strategies being employed in dual-channel memory controllers, one in which where each memory bank has its own memory channel and an arbiter distributes the load between them and the other to actually create a wider memory channel, thereby "doubling up" on standard DDR's 64-bit data paths. In common with the i875P chipset, the i865's Memory Controller Hub employs the latter, the same conditions for dual-channel operation also applying.
The i865 memory controller is the same as that used by the i875P chipset, supporting:
• Hyper Threading
• Dual 64-bit DDR memory channels
• Communication Streaming Architecture bus for gigabit Ethernet
and capable of being paired with either the ICH5 or ICH5R chip - which handles things like the 10/100 Ethernet interface, 6-channel AC97 audio interface, USB 2.0, the PCI bus, etc., to provide the following additional features:
• 8 USB 2.0 ports
• Dual independent Serial ATA ports
The ICH5R also provides software RAID for Serial ATA drives.
The upshot is that - unlike the i875P - i865 chipsets are available in three different versions:
• i865P: supports DDR266 and DDR333 memory only and doesn't support the 800MHz FSB.
• i865PE: as per i865P, plus 800MHz FSB and DDR400 memory support.
• i865G: as per i865PE, plus Intel's integrated graphics core.
While the i865G's graphics core is the same as was featured on the i845G chipset, its performance will be faster, due both to a faster memory subsystem and a higher working frequency of the graphics core itself.
The following table compares a number of major characteristics of the i865P chipset with a selection of Intel's other recent Hyper-Threading chipset offerings
i925X PCI Express chipset
In the summer of 2004 Intel introduced a new family of chipsets that they claimed brought the most profound changes in PC platform architecture in more than a decade. The relative positioning of the chipsets - codenamed Alderwood and Grantsdale - is similar to that of the Canterwood and Springdale chipsets which preceded it. The 925X PCI Express chipset is the higher-end of the two, boasting a number of specific performance enhancements and being designed to deliver the ultimate gaming experience when coupled with Pentium 4 Extreme Edition CPUs.
The new chipsets are designed for use with the latest Prescott-cored Pentium 4 CPUs, designated by the new numeric model naming scheme - initially the 560 at 3.6GHz, down to the 520 at 2.8GHz. They will therefore only be used in motherboards that support Intel's innovative LGA775 package, which facilitates a direct electrical connection between the chip module substrate and the motherboard which the company claims will provide the robust power and signal delivery needed for future performance headroom.
All the new chipsets support Hyper-Threading, an 800MHz FSB and dual-channel DDR2-533 memory and enable a broad spectrum of new platform capabilities:
• Intel High Definition Audio enables multistreaming, 7.1 surround sound and dynamic jack retasking in a groundbreaking PC audio solution that provides performance comparable to high-end consumer electronics (CE) equipment.
• Intel Matrix Storage Technology provides the performance benefits of RAID 0 for media-intensive applications and the added protection of RAID 1 for critical digital media files and data on just two drives.
• The I/O Controller Hub 6 (ICH6R version) supports four 1.5 GBps Serial ATA (SATA) ports with Advanced Host Controller Interface (AHCI) capability, enabling Native Command Queuing for enhanced storage performance.
• Four PCI Express x1 high-speed expansion ports are ready for Gigabit Ethernet and future applications, including multiple TV tuners implemented in a single card.
• Intel Wireless Connect Technology enables users to create or expand a wireless network without external access point hardware. Intel Wireless Connect Technology requires a specific Intel 9XX Express Chipset and a separate Intel wireless LAN solution to operate.
Intel's new Flex memory system introduces some welcome flexibility, with dual-channel operation no longer being restricted to identical memory modules bought in matched pairs. Now the requirement is simply for the same amount of memory - whatever the configuration - in each of the two available banks.
Foremost amongst the innovations is the introduction of the PCI Express (PCX) bus technology. As digital video content becomes ever more important in today’s electronic universe, no single aspect of the personal computing platform requires as much performance increase as the graphics interface.
The new chipsets address this need in the shape of the revolutionary 16x PCI Express graphics interface, as its name implies, an aggregation of 16 lanes. This provides the increased bandwidth and scalability necessary to tackle the most demanding multimedia tasks, with up to four times the theoretical maximum bandwidth over previous generation AGP8X-based solutions - up to 4 GBps of peak bandwidth per direction and up to 8 GBps concurrent bandwidth.
AGP is unceremoniously consigned to history, the new chipsets providing no AGP interface at all. In time 1x PCX will replace the decade-old PCI standard.
i915 Express chipsets
Announced at the same time as the i925X Express", the i915 Express chipset family - codenamed Grantsdale and comprising the i915P and i915G chipsets - have the same features as it's sibling with the exception of some specific performance improvements.
The principal differences between the i915 and i925X chipsets are in graphics and memory support. The i915 supports traditional dual-channel DDR memory as well as the more expensive DDR2 variety. In addition, the i915G chipset includes an integrated Intel Graphics Media Accelerator 900, optimised for Microsoft DirectX 9 and capable of providing dual independent display capability with support for the latest 16:9 ratio monitors, in addition to conventional 4:3 displays.
The 3D graphics pipeline is broken up into four major stages, including geometry processing, setup (vertex processing), texture application and rasterisation. The Intel GMA 900 is optimised to use the Intel Pentium 4 processor for software-based geometry processing (such as transform and lighting) defined by Microsoft DirectX 9.
The Intel GMA 900 handles the remaining three stages, including converting vertices to pixels, applying textures to pixels, and rasterisation — the application of lighting and other effects to produce the final pixel value. From the rasterisation stage the Intel GMA 900 writes the final pixel value to the frame buffer for display. Intel GMA 900 includes two independent display pipelines that enable operation of dual displays.
The Intel GMA 900 utilises a shared memory architecture, its support for dual-channel DDR2/533-MHz memory ensuring the memory bandwidth so critically important for quality and performance.
A chipset or "PCIset" is a group of microcircuits that orchestrate the flow of data to and from key components of a PC. This includes the CPU itself, the main memory, the secondary cache and any devices situated on the ISA and PCI buses. The chipset also controls data flow to and from hard disks, and other devices connected to the IDE channels. While new microprocessor technologies and speed improvements tend to receive all the attention, chipset innovations are, in fact, equally important.
Although there have always been other chipset manufacturers - such as SIS, VIA and Opti - for many years Intel's "Triton" chipsets were by far the most popular. Indeed, the introduction of the Intel Triton chipset caused something of a revolution in the motherboard market, with just about every manufacturer using it in preference to anything else. Much of this was down to the ability of the Triton to get the best out of both the Pentium processor and the PCI bus, together with its built-in master EIDE support, enhanced ISA bridge and ability to handle new memory technologies like EDO and SDRAM. However, the new PCI chipsets" potential performance improvements will only be realised when used in conjunction with BIOSes capable of taking full advantage of the new technologies on offer.
During the late 1990s things became far more competitive, with Acer Laboratories (ALI), SIS and VIA Technologies all developing chipsets designed to operate with Intel, AMD and Cyrix processors. 1998 was a particularly important year in chipset development, with what had become an unacceptable bottleneck - the PC's 66MHz system bus - to finally being overcome. Interestingly, it was not Intel but rival chipmakers that made the first move, pushing Socket 7 chipsets to 100MHz. Intel responded with its 440BX, one of many chipsets to use the ubiquitous Northbridge/Southbridge architecture. It was not long before Intel's hold on the chipset market loosened further still, and again, the company had no-one but itself to blame. In 1999, its single-minded commitment to Direct Rambus DRAM (DRDRAM) left it in the embarrassing position of not having a chipset that supported the 133MHz system bus speed its latest range of processors were capable of. This was another situation it's rivals were able to exploit, and in so doing gain market share.
The following charts the evolution of Intel chipsets over the years, from the time of it's first Triton chipset. During this time there have also been a number of special chipsets optimised for the Pentium Pro or designed for use with notebook PCs.
Triton 430FX
Introduced in early 1995, the 82430FX - to give it its full name - was Intel's first Triton chipset and conformed to the PCI 2.0 specification. It introduced support for EDO memory configurations of up to 128MB and for pipelined burst cache and synchronous cache technologies. However, it did not support a number of emerging technologies such as SDRAM and USB and was superseded in 1996 - little more than a year after its launch - by a pair of higher performance chipsets.
Triton 430VX
The Triton 430VX chipset conforms to the PCI 2.1 specification, and is designed to support Intel's Universal Serial Bus (USB) and Concurrent PCI standards. With the earlier 430FX, a bus master (on the ISA or PCI bus), such as a network card or disk controller, would lock the PCI bus whenever it transferred data in order to have a clear path to memory. This interrupted other processes, and was inefficient because the bus master would never make full use of the 100 MBps bandwidth of the PCI bus. With Concurrent PCI, the chipset can wrest control of the PCI bus from an idle bus master to give other processes access on a timeshare basis. Theoretically, this should allow for data transfer rates of up to 100 MBps, 15% more than the 430FX chipset, and smooth intensive PCI tasks such as video playback when bus masters are present.
The 430VX chipset was aimed fairly and squarely at the consumer market. It was intended to speed up multimedia and office applications, and it was optimised for 16-bit. Furthermore, it was designed to work with SDRAM, a special type of memory that's optimised for intensive multimedia processing. Although the performance gains are slight for this type of RAM over EDO RAM, the advantage is that it can operate efficiently from a single Dual In-line Memory Module (DIMM) and does not need to be paired.
The 430VX provided improved EDO memory timings which was supposed to allow cacheless systems to be built without compromising performance, at least compared to a PC with asynchronous cache. In practice, though, most manufacturers continued to provide at least some secondary cache, with most using synchronous cache to maximise performance.
Triton 430HX
The Triton 430HX chipset is geared towards business machines and was developed with networking, video conferencing and MPEG video playback in mind. It supports multiple processors, has been optimised for 32-bit operation and to work with large memory arrays (up to 512MB) and provides error control (ECC) facilities on the fly when 32-bit parity SIMMs are used. The 430HX does not support SDRAM.
The biggest difference between the HX and VX chipsets is the packaging. Where the VX consists of four separate chips, all built using the traditional plastic quad flat packaging, the HX chipset comprises just two chips, the 82439HX System Controller (SC), which manages the host and PCI buses, and the 82371SB PIIX3 for the ISA bus and all the ports.
The SC comes in a new ball grid array (BGA) packaging which reduces overall chip size and makes it easier to incorporate onto motherboard designs. It exerts the greatest influence on the machine's CPU performance, as it manages communications between the CPU and memory. The CPU has to be fed data from the secondary cache as quickly as possible, and if the necessary data isn"t already in the cache, the SC fetches it from main memory and loads it into the cache. The SC also ensures that data written into cache by the CPU is "flushed" back into main memory.
The PIIX3 chip manages the many processes involved in getting data into and out of RAM from the other devices in the PC. It provides two EIDE channels, both of which can accept two drives. IDE drives contain most of the controlling circuitry built into the hard disk itself, so the PIIX is mainly responsible for shifting data from the drives into RAM and back as quickly as possible. It also provides two 115,200bit/s buffered serial ports, an error correcting Enhanced Parallel Port, a PS/2 mouse port and a keyboard controller. The PIIX also supports additional connections that many motherboards have yet to adopt as the norm, such as a Universal Serial Bus connector and an infrared port.
Triton 430TX
The Triton 430TX includes all the features found on the earlier chipsets, including Concurrent PCI, USB support, aggressive EDO RAM timings and SDRAM support and is optimised for MMX processors and is designed to be used in both desktop and mobile computers.
The Triton 430TX also continues the high-integration two-chip BGA packaging first seen with the 430HX chipset, comprising the 82439TX System Controller (MTXC) and the 82371AB PCI ISA IDE Xcelerator (PIIX4). The former integrates the cache and main memory DRAM control functions and provides bus control to transfers between the CPU, cache, main memory, and the PCI Bus. The latter is a multi-function PCI device implementing a PCI-to-ISA bridge function, a PCI IDE function, a Universal Serial Bus host/hub function, and an Enhanced Power Management function.
The diagram below provides an overview of the overall architecture and shows the division of functionality between the System Controller and the Peripheral Bus Controller components - which are often referred to as "Northbridge" and "Southbridge" chipsets respectively.
The TX incorporates the Dynamic Power Management Architecture (DPMA) which reduces overall system power consumption and offers intelligent power-saving features like suspend to RAM and suspend to disk. The TX chipset also supports the new Ultra DMA disk protocol which enables a data throughput of 33 MBps from the hard disk drive to enhance performance in the most demanding applications.
440LX
The 440LX (by this time Intel had dropped the term "Triton") was the successor to the Pentium Pro 440FX chipset and was developed by Intel to consolidate on the critical success of the Pentium II processor launched a few months earlier. The most important feature of the 440LX is support for the Accelerated Graphics Port (AGP), a new, fast, dedicated bus designed to eliminate bottlenecks between the CPU, graphics controller and system memory, which will aid fast, high-quality 3D graphics.
Other improvements with the LX are more like housekeeping, bringing the Pentium II chipset up to the feature set of the 430TX by providing support for SDRAM and Ultra DMA IDE channels. The chipset includes the Advanced Configuration and Power Interface (ACPI), allowing quick power down and up, remote start-up over a LAN for remote network management, plus temperature and fan speed sensors. The chipset also has better integration with the capabilities of the Pentium II, such as support for dynamic execution and processor pipelining.
440EX
The 440EX AGPset, based on the core technology of the 440LX AGPset, is designed for use with the Celeron family of processors. It is ACPI-compliant and extends support for a number of advanced features such as AGP, UltraDMA/33, USB and 66MHz SDRAM, to the "Basic PC" market segment.
440BX
The PC's system bus had been a bottleneck for too long. Manufacturers of alternative motherboard chipsets had made the first move, pushing Socket 7 chipsets beyond Intel's 66MHz. Intel's response came in April 1998, with the release of its 440BX chipset, which represented a major step in the Pentium II architecture. The principal advantage of the 440BX chipset is support for a 100MHz system bus and 100MHz SDRAM. The former 66MHz bus speed is supported, allowing the BX chipset to be used with older (233MHz-333MHz) Pentium IIs.
The 440BX chipset features Intel's Quad Port Acceleration (QPA) to improve bandwidth between the Pentium II processor, the Accelerated Graphics Port, 100-MHz SDRAM and the PCI bus. QPA combines enhanced bus arbitration, deeper buffers, open-page memory architecture and ECC memory control to improve system performance. Other features include support for dual processors, 2x AGP, and the Advanced Configuration Interface (ACPI).
440ZX
The 440ZX is designed for lower cost form factors without sacrificing the performance expected from an AGPset, enabling 100MHz performance in form factors like microATX. With footprint compatibility with the 440BX, the 440ZX is intended to allow OEMs to leverage BX design and validation investment to produce new systems to meet entry level market segment needs.
440GX
Released at the same time as the Pentium II Xeon processor in mid-1998, the 440GX chipset was an evolution of the 440BX AGPset intended for use with Xeon-based workstations and servers. Built around the core architecture of its 440BX predecessor, the 440GX includes support for both Slot 1 and Slot 2 implementations, a 2x AGP expansion slot, dual CPUs and a maximum of 2GB of memory.
Importantly, the chipset supports full speed backside bus operation, enabling the Pentium II Xeon's Level 2 cache to run at the same speed as the core of the CPU.
810 AGPset
Formerly codenamed "Whitney", the 810 AGPset finally reached the market in the summer of 1999. It is a three-chip solution comprising the 82810 Graphics Memory Controller Hub (GMCH), 82801 I/O Controller Hub (ICH) and 82802 Firmware Hub (FWH) for storing the system and video BIOS. A break from tradition is that these components don't communicate with each other over the PCI bus. Instead, they use a dedicated 8-bit 266 MBps proprietary bus, thereby taking load off the PCI subsystem. The SDRAM memory interface is also unusual in that it runs at 100MHz irrespective of the system bus speed. There's no ISA support, but it could be implemented if a vendor added an extra bridge chip.
At the time of its launch, there were two versions of the 810 - the 82810 and 81810-DC100. The former is 66MHz part with no graphics memory, while the latter is a 100MHz-capable chip with support for 4MB of on-board graphics memory. The Direct AGP graphics architecture uses 11MB of system memory for frame buffer, textures and Z-buffer if no display cache is implemented. This drops to 7MB if the display cache is implemented. The whole configuration is known as Direct Video Memory technology. Also incorporated in the chipset is an AC-97 CODEC, which allows software modem and audio functionality. Vendors can link this to an Audio Modem Riser (AMR) slot to facilitate future plug-in audio or modem upgrades.
In the autumn of 1999 a subsequent version of the chipset - the 810E - extended support processors with a 133 MHz system bus. The Intel 810E chipset features a unique internal gear arbitration, allowing it to run seamlessly with 66 MHz, 100 MHz and 133 MHz processor busses.
As the cost of processors come down, the marginal costs of the motherboard, graphics and sound subsystems becomes an increasingly important factor in vendors' efforts to hit ever-lower price points. However, high levels of integration can be a double-edged sword: it reduces vendors' bill-of-materials (BOM) costs, but also limits their capability for product differentiation. Many manufacturers defer their decisions on graphics and sound options to late in the production cycle in order to maintain a competitive marketing advantage. Given that other highly integrated solutions - such as Cyrix's Media GX - haven't fared particularly well in the past, the 810 AGPset represents a bold move on Intel's part and one that signals the company's determination to capture a greater share of the "value PC" market which had been effectively ceded to AMD and Cyrix over the prior couple of years.
820 chipset
Originally scheduled to be available concurrently with the Pentium III processor in the spring of 1999, Intel's much delayed 820 chipset was finally launched in November that year. Those delays - which had left Intel in the position not having a chipset that supported the 133MHz system bus speed their latest range of processors were capable of - were largely due to delays in the production of Direct Rambus DRAM (DRDRAM), a key component in Intel's 133MHz platform strategy.
Direct RDRAM memory provides a memory bandwidth capable of delivering 1.6 GBps of maximum theoretical memory bandwidth - twice the peak memory bandwidth of 100MHz SDRAM systems. Additionally, the 820's support for AGP 4x technology allows graphics controllers to access main memory at more than 1 GBps - twice that of previous AGP platforms. The net result is the significantly improved graphics and multimedia handling performance expected to be necessary to accommodate future advances in both software and hardware technology.
The 820 chipset employs the Accelerated Hub Architecture that is offered in all Intel 800 series chipsets - the first chipset architecture to move away from the traditional Northbridge /Southbridge design. It supports a bandwidth of 266 MBps and, with it's optimised arbitration rules which allow more functions to run concurrently, delivers significantly improved audio and video handling. The chipset's three primary components are:
• Memory Controller Hub
• I/O Controller Hub, and
• Firmware Hub.
The Memory Controller Hub provides a high-performance interface for the CPU, memory and AGP and supports up to 1GB of memory via a single channel of RDRAM using 64-, 128- and 256-Mbit technology. With an internal bus running at 1.6 GBps and an advanced buffering and queuing structure, the Memory Hub Controller balances system resources and enables concurrent processing in either single or dual processor configurations.
The I/O Controller Hub forms a direct connection from the PC's I/O devices to the main memory. This results in increased bandwidth and significantly reduced arbitration overhead, creating a faster path to main memory. To capitalise further on this faster path to main memory, the 820 chipset features an integrated AC97 controller in addition to an ATA66 drive controller, dual USB ports and PCI add-in cards.
The Firmware Hub stores system and video BIOS and includes a first for the PC platform - a hardware-based random number generator. The Intel RNG provides truly random numbers through the use of thermal noise - thereby enabling stronger encryption, digital signing and security protocols. This is expected to be of particular benefit to the emerging class of e-commerce applications.
The i820 hadn't long been on the market before Intel - recognising that the price of RDRAM was likely to remain high for sometime - designed and released an add-on chip, the 82805 Memory Translator Hub (MTH), which, when implemented on the motherboard, allowed the use of PC100 SDRAM. Sitting between the i820's Memory Controller Hub (MCH) and the RDRAM memory slots, the MTH chip translates the Rambus memory protocol that's used by RDRAM into the parallel protocol required by SDRAM, thereby allowing the i820 to use this much more price attractive memory.
Within a few months, a bug in the MTH component came to light. This was serious enough to cause Intel to recall all MTH-equipped i820-motherboards. Since it wasn't possible to replace the defective chip Intel took the extraordinary step of giving every owner of an MTH-equipped i820 motherboard a replacement non-MTH motherboard as well as RDRAM to replace the SDRAM that was used before!
815 chipset
The various problems that had so delayed the introduction of Direct Rambus DRAM (DRDRAM), finally resulted in Intel doing what it had been so reluctant to do for so long - release a chipset supporting PC133 SDRAM. In fact, in mid-2000, it announced two such chipsets - formerly codenamed "Solano" - the 815 Chipset and the 815E Chipset.
Both chipsets use Intel's Graphics and Memory Controller Hub (GMCH). This supports both PC133 and PC100 SDRAM and provides onboard graphics, with a 230MHz RAMDAC and limited 3D acceleration. This gives system integrators the option of using the on-board graphics - and system memory - for lower cost systems or upgrading via an external graphics card for either AGP 4x or AGP 2x graphics capabilities.
Additionally, and like the 820E Chipset before it, the 815E features a new I/O Controller Hub (ICH2) for greater system performance and flexibility. This provides an additional USB controller, a Local Area Network (LAN) Connect Interface, dual Ultra ATA /100 controllers and up to six-channel audio capabilities. Integrating a Fast Ethernet controller directly into the chipsets makes it easier for computer manufacturers and system integrators to implement cost-effective network connections into PCs. The ICH2's enhanced AC97 interface supports full surround-sound for Dolby Digital audio found on DVD and simultaneously supports a soft modem connection.
850 chipset
Designed in tandem with the Pentium 4 processor, Intel's 850 Chipset represents the next step in the evolution of the Intel Hub Architecture, the successor to the previous northbridge /southbridge technology first seen on the 810 Chipset. Comprising the 82850 Memory Controller Hub (MCH) and 82801BA I/O Controller Hub (ICH2), the new chipset's principal features are:
• a 400MHz system bus
• dual RDRAM memory channels, operating in lock step to deliver 3.2 GBps of memory bandwidth to the processor
• support for 1.5V AGP4x technology, allowing graphics controllers to access main memory at over 1 GBps - twice the speed of previous AGP platforms
• two USB controllers, doubling the bandwidth available for USB peripherals to 24 MBps over four ports
• dual Ultra ATA/100 controllers support the fastest IDE interface for transfers to storage devices.
To ensure maximum performance, the system bus is balanced with the dual RDRAM channels at 3.2 GBps, providing 3x the bandwidth of platforms based on Intel III processors and allowing better concurrency for media-rich applications and multitasking.
In the autumn of 2002, some 18 months after the i850 was first introduced, the i850E variant was released, extending the capabilities of the chipset to support Hyper-Threading, a 533MHz system bus and PC1066 memory, for Pentium 4 class processors.
i845 chipset
The fact that system builders were obliged to use expensive DRDRAM - by virtue of the absence of any Pentium 4 chipsets supporting conventional SDRAM - had been an issue ever since the Pentium 4's launch at the end of 2000. The situation changed during the course of 2001, with chipmakers SiS and VIA both releasing Pentium 4 chipsets with DDR SDRAM support. Although this was a move of which Intel disapproved, it did have the effect of boosting the appeal of the Pentium 4, whose sales hitherto had been disappointing.
In the summer of 2001 Intel eventually gave in to market pressures and released their 845 chipset - previously codenamed "Brookdale" - supporting Pentium 4 systems' use of PC133 SDRAM. Whilst the combination of i845 and PC133 SDRAM meant lower prices - given that the speed of the memory bus was about three times slower than that of the Pentium 4 system bus - it also meant significantly poorer performance than that of an i850/DRDRAM based system. The reason the i845 didn't support faster DDR SDRAM at this time was apparently because they were prevented from allowing this until the start of the following year by the terms of a contract they'd entered into with Rambus, the inventors of DRDRAM.
Sure enough, at the beginning of 2002 re-released of the i845 chipset. The new version - sometimes being referred to as i845D - differs from its predecessor only in respect of its memory controller, which now supports PC1600 and PC2100 SDRAM - sometimes referred to as DDR200 and DDR266 respectively - in addition to PC133 SDRAM. It had reportedly been Intel's original intention for the i845 chipset to support only DDR200 SDRAM - capable of providing a maximum bandwidth of 1600MBps. However, the boom in the use of DDR SDRAM - and the consequent dramatic fall in prices - caused a rethink and the subsequent decision to extend support to DDR266 (maximum bandwidth 2100MBps). The fact that the company was prepared to make this decision even though it was bound to adversely impact the market share of its i850 chipset appears to indicate that the company's apparent infatuation with DRDRAM is well and truly over.
The 400MHz system bus of the i845 solution enables up to 3.2GBps of memory bandwidth to Pentium 4 processor. Compare this with the up to 1 GBps of data transfer possible from PC133 SDRAM and it is clear why faster DDR SDRAM makes such a difference to overall system performance. Its 1.5V 4x AGP interface with provides over 1 GBps of graphics bandwidth. Other features of the i845 chipset include an 4x AGP interface, 133MBps to the PCI, support for four USB ports, six-channel audio, a generally unused LAN connect interface, dual ATA-100 controllers and CNR support.
The i845 is Intel's first chipset to use a Flip Chip BGA packaging for the chip itself. This improves heat conductivity between the Memory & Controller Hub (MCH) and its heatsink which is required for proper operation. It is also the first MCH built using a 0.18-micron process; earlier versions have been 0.25-micron. The smaller die allows another first - the incorporation of a Level 3-like write cache, significantly increasing the speed at which the CPU is able to write data. It is expected that the transition to 0.13-micron MCH/Northbridges will enable this idea to be further developed, to the point where chipsets include much larger, genuine Level 3 caches on the MCH itself. The i845 further capitalises on the performance advantage realised by its high-speed write cache by the provision of deep data buffers. These play an important role in assisting the CPU and write cache to sustain its high data throughput levels.
A number of newer versions of the i845 chipset were subsequently released, all supporting the USB 2.0 interface (which increases bandwidth up to 40 times over the previous USB 1.1 standard):
• The i845G chipset, incorporating a new generation of integrated graphics - dubbed Intel Extreme Graphics - and targeted at the high-volume business and consumer desktop market segments.
• The i845E chipset, which works with discrete graphics components
• The i845GL chipset, designed for Celeron processor-based PCs.
i845GE chipset
The i845GE chipset was designed and optimised to support Hyper-Threading, Intel's innovative technology that achieves significant performance gains by allowing a single processor to be treated as two logical processors. Whilst not the first i845 chipset to support HT technology, it was the first in which that support was actually implemented, being launched at the same time as the first Intel's first HT-enabled desktop CPU, the 3.06GHz Pentium 4 unveiled in late 2002.
As well as supporting a faster, 266MHz version of Intel's Extreme Graphics core, the i845GE also supports a system bus speed of either 400 or 533MHz, up to DDR333 main memory and offers maximum display (digital CRT or TV) flexibility through an AGP4x connector.
The i845PE and i845GV chipsets are lower-spec variants of the i845GE, the former having no integrated graphics and the latter limiting both the Intel Extreme Graphics core and main memory support to DDR266 SDRAM.
Intel E7205 chipset
At the end of 2002, Intel announced the launch of a dozen Intel Xeon processor family products, including new processors, chipsets and platforms for Intel-based servers and workstations. Amongst these was one single-processor chipset, the E7205, formerly codenamed Granite Bay.
For some time the most viable way of balancing the bandwidth between the Pentium 4 CPU and its memory subsystem had been to couple the i850E chipset with dual-channel RDRAM. However, given the price and availability issues surrounding high-density RDRAM modules, this was a far from ideal solution. Despite - as it's server/workstation class chipset nomenclature implies - not originally being intended for desktop use, the E7205 chipset was to provide an answer to this dilemma. With a specification which includes support for:
• Dual Channel DDR266 memory bus (4.2GBps memory bandwidth)
• 400/533MHz FSB support (3.2GBps - 4.2GBps FSB bandwidth)
• AGP 8x
• USB 2.0, and
• integrated LAN.
it didn't take long for the motherboard manufacturers to produce boards based on the new chipset.
The E7205's memory controller is fully synchronous, meaning that the memory in E7205-based motherboards is clocked at the rate equal to the FSB frequency. Consequently, only DDR200 SDRAM may be used with CPUs supporting a 400MHz FSB and only DDR266 SDRAM with processors supporting a 533MHz FSB. The E7205 does not support DDR333 SDRAM.
With the Pentium 4 family destined to make the transition to a 800MHz Quad Pumped Bus - at which time the CPU's bus bandwidth will increase to 6.4GBps - it appears reasonable to assume that the likely way for memory subsystems to have comparable bandwidth will be the continued use of dual-channel DDR SDRAM. To that extent, the E7205 can be viewed as a prototype of the Canterwood and Springdale chipsets slated to appear in 2003.
i875P chipset
Originally, Intel had planned to introduce a 800MHz FSB in the context of the Prescott, the upcoming 90nm Pentium 4 core. However, in the event this was brought forward to the spring of 2003. The rationale was to extend the Pentium 4's performance curve within the confines of their current 0.13-micron process, without having to increase clock speeds to unsustainable levels. The transition from 533MHz to 800MHz FSB was aided and abetted by an associated new chipset platform, the 875P chipset, formerly codenamed Canterwood.
A 64-bit 800MHz FSB provides 6.4GBps of bandwidth between the Memory Controller Hub (or Northbridge) and the CPU. In a move that appears to further reduce the strategic importance of DRDRAM in Intel's product planning, and that had been signalled by the earlier E7205 chipset, the memory subsystem the 875P uses to balance bandwidth between the Memory Controller Hub (MCH) and memory banks is dual channel DDR SDRAM, all of the DDR400, DDR333 and DD266 variants.
Currently, there are two different strategies being employed in dual-channel memory controllers, one in which where each memory bank has its own memory channel and an arbiter distributes the load between them and the other to actually create a wider memory channel, thereby "doubling up" on standard DDR's 64-bit data paths. The i875P employs the latter technique, with each pair of installed DIMMs acting as a 128-bit memory module, able to transfer twice as much data as a single-channel solution, without the need for an arbiter.
As a consequence, dual channel operation is dependent on a number of conditions being met, Intel specifying that motherboards should default to single-channel mode in the event of any of these being violated:
• DIMMs must be installed in pairs
• Both DIMMs must use the same density memory chips
• Both DIMMs must use the same DRAM bus width
• Both DIMMs must be either single-sided or dual-sided.
The 875P chipset also introduces two significant platform innovations:
• Intel Performance Acceleration Technology (PAT), and
• Communications Streaming Architecture (CSA).
PAT optimises memory access between the processor and system memory for platforms configured with both the new 800Mhz FSB and Dual-Channel DDR400 memory. CSA is a new communications architecture that creates a dedicated link from the Memory Controller Hub (MCH) to the network interface, thereby offloading network traffic from the PCI bus. Used in conjunction with the new Intel PRO/1000 CT Desktop Connection gigabit Ethernet controller, it is claimed that CSA doubles the networking bandwidth possible with traditional PCI bus-based solutions.
Additionally, the 875P chipset includes a high-performance AGP 8x graphics interface, integrated Hi-Speed USB 2.0, optional ECC is supported for users that demand memory data reliability and integrity and dual independent DMA audio engines, enabling a user to make a PC phone call whilst at the same time playing digital music streams. The chipset is also Intel's first to offer native Serial ATA (SATA), a special version designated by the "-R" suffix adding RAID - albeit only RAID 0 (data striping) - support.
i865 chipset
If the i875 chipset can be viewed as the logical successor to i850E, then it's mainstream variant, the i865 chipset - formerly codenamed Springdale - can be viewed as the logical successor to the i845 series of chipsets. Not only do the i875/i865 chipsets represent a huge technological leap compared to their predecessors, but the performance gap between the pair of recent chipsets is significantly less than it was between the i850E and i845 family.
There is a clear trend in PC hardware towards parallel processes, epitomised by Intel's Hyper-Threading technology. However, there are other examples of where performing several tasks at the same time is preferable to carrying out a single task quickly. Hence the increasing popularity of small RAID arrays and now the trend towards dual-channel memory subsystems.
Currently, there are two different strategies being employed in dual-channel memory controllers, one in which where each memory bank has its own memory channel and an arbiter distributes the load between them and the other to actually create a wider memory channel, thereby "doubling up" on standard DDR's 64-bit data paths. In common with the i875P chipset, the i865's Memory Controller Hub employs the latter, the same conditions for dual-channel operation also applying.
The i865 memory controller is the same as that used by the i875P chipset, supporting:
• Hyper Threading
• Dual 64-bit DDR memory channels
• Communication Streaming Architecture bus for gigabit Ethernet
and capable of being paired with either the ICH5 or ICH5R chip - which handles things like the 10/100 Ethernet interface, 6-channel AC97 audio interface, USB 2.0, the PCI bus, etc., to provide the following additional features:
• 8 USB 2.0 ports
• Dual independent Serial ATA ports
The ICH5R also provides software RAID for Serial ATA drives.
The upshot is that - unlike the i875P - i865 chipsets are available in three different versions:
• i865P: supports DDR266 and DDR333 memory only and doesn't support the 800MHz FSB.
• i865PE: as per i865P, plus 800MHz FSB and DDR400 memory support.
• i865G: as per i865PE, plus Intel's integrated graphics core.
While the i865G's graphics core is the same as was featured on the i845G chipset, its performance will be faster, due both to a faster memory subsystem and a higher working frequency of the graphics core itself.
The following table compares a number of major characteristics of the i865P chipset with a selection of Intel's other recent Hyper-Threading chipset offerings
i925X PCI Express chipset
In the summer of 2004 Intel introduced a new family of chipsets that they claimed brought the most profound changes in PC platform architecture in more than a decade. The relative positioning of the chipsets - codenamed Alderwood and Grantsdale - is similar to that of the Canterwood and Springdale chipsets which preceded it. The 925X PCI Express chipset is the higher-end of the two, boasting a number of specific performance enhancements and being designed to deliver the ultimate gaming experience when coupled with Pentium 4 Extreme Edition CPUs.
The new chipsets are designed for use with the latest Prescott-cored Pentium 4 CPUs, designated by the new numeric model naming scheme - initially the 560 at 3.6GHz, down to the 520 at 2.8GHz. They will therefore only be used in motherboards that support Intel's innovative LGA775 package, which facilitates a direct electrical connection between the chip module substrate and the motherboard which the company claims will provide the robust power and signal delivery needed for future performance headroom.
All the new chipsets support Hyper-Threading, an 800MHz FSB and dual-channel DDR2-533 memory and enable a broad spectrum of new platform capabilities:
• Intel High Definition Audio enables multistreaming, 7.1 surround sound and dynamic jack retasking in a groundbreaking PC audio solution that provides performance comparable to high-end consumer electronics (CE) equipment.
• Intel Matrix Storage Technology provides the performance benefits of RAID 0 for media-intensive applications and the added protection of RAID 1 for critical digital media files and data on just two drives.
• The I/O Controller Hub 6 (ICH6R version) supports four 1.5 GBps Serial ATA (SATA) ports with Advanced Host Controller Interface (AHCI) capability, enabling Native Command Queuing for enhanced storage performance.
• Four PCI Express x1 high-speed expansion ports are ready for Gigabit Ethernet and future applications, including multiple TV tuners implemented in a single card.
• Intel Wireless Connect Technology enables users to create or expand a wireless network without external access point hardware. Intel Wireless Connect Technology requires a specific Intel 9XX Express Chipset and a separate Intel wireless LAN solution to operate.
Intel's new Flex memory system introduces some welcome flexibility, with dual-channel operation no longer being restricted to identical memory modules bought in matched pairs. Now the requirement is simply for the same amount of memory - whatever the configuration - in each of the two available banks.
Foremost amongst the innovations is the introduction of the PCI Express (PCX) bus technology. As digital video content becomes ever more important in today’s electronic universe, no single aspect of the personal computing platform requires as much performance increase as the graphics interface.
The new chipsets address this need in the shape of the revolutionary 16x PCI Express graphics interface, as its name implies, an aggregation of 16 lanes. This provides the increased bandwidth and scalability necessary to tackle the most demanding multimedia tasks, with up to four times the theoretical maximum bandwidth over previous generation AGP8X-based solutions - up to 4 GBps of peak bandwidth per direction and up to 8 GBps concurrent bandwidth.
AGP is unceremoniously consigned to history, the new chipsets providing no AGP interface at all. In time 1x PCX will replace the decade-old PCI standard.
i915 Express chipsets
Announced at the same time as the i925X Express", the i915 Express chipset family - codenamed Grantsdale and comprising the i915P and i915G chipsets - have the same features as it's sibling with the exception of some specific performance improvements.
The principal differences between the i915 and i925X chipsets are in graphics and memory support. The i915 supports traditional dual-channel DDR memory as well as the more expensive DDR2 variety. In addition, the i915G chipset includes an integrated Intel Graphics Media Accelerator 900, optimised for Microsoft DirectX 9 and capable of providing dual independent display capability with support for the latest 16:9 ratio monitors, in addition to conventional 4:3 displays.
The 3D graphics pipeline is broken up into four major stages, including geometry processing, setup (vertex processing), texture application and rasterisation. The Intel GMA 900 is optimised to use the Intel Pentium 4 processor for software-based geometry processing (such as transform and lighting) defined by Microsoft DirectX 9.
The Intel GMA 900 handles the remaining three stages, including converting vertices to pixels, applying textures to pixels, and rasterisation — the application of lighting and other effects to produce the final pixel value. From the rasterisation stage the Intel GMA 900 writes the final pixel value to the frame buffer for display. Intel GMA 900 includes two independent display pipelines that enable operation of dual displays.
The Intel GMA 900 utilises a shared memory architecture, its support for dual-channel DDR2/533-MHz memory ensuring the memory bandwidth so critically important for quality and performance.