SiS, the Ali Corporation, ATI, and VIA all produce chipsets for the Intel Pentium 4 and Celeron 4 processors.

Although Intel's chipsets for the Pentium 4 have dominated the market up to this point, many of these chipsets offer unique features that are worth considering. The following sections discuss these chipsets by vendor.

High-Speed North-South Bridge Connections

As you learned earlier in this chapter, Intel has developed a replacement for the traditional North Bridge/South Bridge architecture known as hub architecture.

This 266MBps interface provides a faster connection between the memory controller hub/graphics memory controller hub (North Bridge replacements) and the I/O controller hub (South Bridge replacements) in Intel 8xx-series chipsets for the Pentium III and Pentium 4 processor families.

Intel is not alone in replacing the slow PCI bus connection between North and South Bridge–type chips with a faster architecture that bypasses the PCI bus. Other companies introducing high-speed chipset interconnects include:

• VIA. It created the V-Link architecture to connect its North and South Bridge chips at speeds matching or exceeding Intel hub architecture. V-Link uses a dedicated 8-bit data bus and is currently implemented in two versions: 4x V-Link and 8x V-Link. 4x V-Link transfers data at 266MBps (4x66MHz), which is twice the speed of PCI and matches the speed of Intel's hub architecture.

8x V-Link transfers data at 533MBps (4x133MHz), which is twice the speed of Intel's hub architecture. All VIA South Bridge chips in the VT82xx series support V-Link. The first chipsets to use V-Link were VIA's 266-series chipsets for the Pentium III, Pentium 4, and Athlon processor families. VIA's 333- and 400-series chipsets also use V-Link.

• SiS. Its MuTIOL architecture provides performance comparable to VIA's 4x V-Link. Chipsets that support MuTIOL use separate address, DMA, input data, and output data buses for each I/O bus master. MuTIOL buffers and manages multiple upstream and downstream data transfers over a bidirectional 16-bit data bus.

South Bridge chips in the SiS961 and 962 series support MuTIOL at a data transfer rate of 533MBps (133MHzx4), whereas the SiS963 series supports the faster MuTIOL 1G, which supports data transfer rates exceeding 1GBps. The North Bridge chips that support MuTIOL are described in the sections listing SiS chipsets for Pentium 4 and Athlon-series processors.

• ATI. It uses a high-speed interconnect called A-Link in some of its IGP integrated chipsets. A-Link runs at 266MBps, matching Intel's hub architecture and first-generation V-Link and MuTIOL designs. Its RS- and RX-series chipsets use the HyperTransport bus.

HyperTransport, which is now developed and managed by the nonprofit HyperTransport Technology Consortium, uses a packetized point-to-point interconnect IP bus that uses low voltage differential signaling. The 8x8 version of HyperTransport used by some ATI chipsets supports 800MHz clock speeds and a data transfer rate of 1.6GBps.

• NVIDIA. Its nForce, nForce2, and nForce3 chipsets use the HyperTransport bus originally developed by AMD.

Although the terms North Bridge and South Bridge continue to be used for chipsets using V-Link, MuTIOL, A-Link, or HyperTransport interconnects between these chipset components, these chipsets really use a hub-based architecture similar to Intel 8xx-series chipsets and receive corresponding boosts in performance as a consequence.

SiS Chipsets for Pentium 4

SiS offers several chipsets for the Pentium 4, including integrated chipsets, chipsets for use with discrete video accelerator cards, and one that supports Rambus RDRAM.

Unlike most of the chipsets SiS has created for the Pentium II/III/Celeron, the SiS chipsets for the Pentium 4 use one of several high-speed South Bridge equivalents (SiS 96x series Media I/O chips) instead of integrating North and South Bridge functions into a single chip.

SiS North and South Bridge chips for the Pentium 4 use a high-speed 16-bit connection known as MuTIOL (Multi-Threaded I/O Link) instead of the slow PCI bus as with older chipsets.

SiS650/651 Chipsets

The SiS650 and 651 chipsets enable Pentium 4 system builders to create low-cost systems with onboard video that can be enhanced with AGP 4x video cards at a later date. The integrated video features support for high-quality DVD playback and the optional SiS301B video bridge for TV-out and DVI LCD panels.

Both chipsets also feature SiS's own MuTIOL technology for connecting the North Bridge and South Bridge chips with a three-layer high-speed (266MHz/533MBps bandwidth) data highway.

The 650 and 651 both support SDRAM and DDR SDRAM, and the 651 adds support for DDR333 memory, the 533MHz system bus of the latest Pentium 4 processors, and hyper-threading in its B-stepping version.

The 650's SiS961 South Bridge provides USB 1.1, ATA-100 (133 in its 961B version), AC'97 six-channel audio, and integrated Ethernet/HomePNA networking. The 651 also uses the newer SiS962 South Bridge, which provides ATA133 and USB 2.0 support.

SiS645/645DX

The 645 family of SiS chipsets does not include the integrated graphics of the 65x family, but they are otherwise similar. They support SDRAM and DDR SDRAM, AGP 4x, and the high-speed MuTIOL North Bridge/South Bridge interface. The 645DX supports DDR333 memory, the 533MHz system bus, and the HT technologies found in the most recent Pentium 4 processors.

Both the 645 and 645DX use the SiS961 South Bridge.

SiS648/655

The SiS648 chipset is a development of the 645DX chipset, with the following differences:

• Supports DDR memory only (up to DDR333)

• 8X AGP slot

• SiS963 South Bridge (USB 2.0, IEEE-1394a support)

The 655 chipset is essentially a dual-channel version of the 648, supporting up to 4GB of memory with DDR266/333 memory only.

SiS R658

The SiS R658 is the first SiS chipset ever to support Rambus RDRAM. Other features include

• Support for Pentium 4 processors with 533MHz and HT (B-stepping only) features

• Dual-channel support for PC1066/PC800 RDRAM (requires identical pairs of memory)

• 4GB maximum memory size

• AGP 8x interface

• MuTIOL 1G (533MHz clock speed providing more than 1GBps throughput) interface to the SiS963 South Bridge

Essentially, the R658 is an RDRAM version of the 655 chipset, and, like the 655, it uses the SiS963 South Bridge.

ALi Corporation Chipsets for Pentium 4

ALi Corporation (formerly known as Acer Laboratories) has produced several chipsets for the Pentium 4 and Celeron 4 processors.

Aladdin P4

The ALi Aladdin P4 was ALi's first Pentium 4-compatible chipset. Because it uses the same M1535-series South Bridge chips used by its earlier Pentium and Pentium II/III chipsets, the P4 is a traditional North Bridge/South Bridge solution. Thus, it relies on the slow (133MBps) PCI interface to carry data between the bridge chips.

The P4's major features include the following:

• 400MHz system bus

• Support for PC100/133 and DDR200/266/333 memory

• ATA-133 support (when used with the M1535D+ South Bridge)

• AGP 4x interface

• USB 1.1 ports

• ACPI power management

The P4 is also available in a version for notebook computers: the ALADDiN-P4M, which uses the D1535+ South Bridge.

M1581/M1563

ALi's M1581/M1563 chipset for the Pentium 4 processor brings ALi's offerings in line with the latest from other chipset vendors. In a break with ALi tradition, it uses the HyperTransport high-speed direct connection between North and South Bridge chips instead of relying on the PCI bus, as with previous designs.

Its major features include

• Support for hyper-threading and 533MHz system bus

• Support for DDR memory up to DDR400 and PC100/133 SDRAM

• ATA-133

• USB 2.0

• AGP 8x interface

• Memory Stick and SD (Secure Digital) flash memory device interfaces

• ACPI power management

• HyperTransport high-speed link between North and South Bridge chips, running at >400MBps bandwidth in each direction (800MBps total throughput)

ATI Chipsets for Pentium 4

ATI's line of chipsets for the Pentium 4 integrate Radeon VE-level 3D graphics, DVD playback, and dual-display features with high-performance North Bridge and South Bridge designs. ATI uses its high-speed A-Link bus to connect its North and South Bridge chips, but it also supports connections to third-party South Bridge chips via the PCI bus.

This enables system designers to create an all-ATI or a mix-and-match solution. Many of the first Radeon IGP-based systems on the market actually used ALi or VIA South Bridge chips.

The Radeon IGP North Bridge chips for Pentium 4 include

• Radeon IGP 330 (uses IXP-series or third-party South Bridge)

• Radeon IGP 340 (uses IXP-series or third-party South Bridge)

• RS250 (uses SB-series)

• RS300 (uses SB-series)

• RS300VE (uses SB-series)

ATI's South Bridge chips include

• IXP 200 (for IGP series)

• IXP 250 (for IGP series)

• SB300C (for RS series)

• SB380 (for RS series)

• SB210 (for RS series)

VIA Chipsets for Pentium 4

Although VIA Technologies produces a line of chipsets for the Pentium 4, it lacks a license from Intel for the Socket 478 interface. VIA claims rights to Socket 478 through a patent exchange agreement with Intel, but Intel disputes this.

As a result of the legal battles over the VIA chipsets for Pentium 4, most of the motherboards that use VIA's chipsets are manufactured by VIA's Platform Solutions Division (VPSD), although they might be sold under a variety of brand names.

All chipsets that use these South Bridge chips use VIA's high-speed V-Link interface between North and South Bridge chips. These chipsets connect to the VT1211 LPC (low pin count) or equivalent Super I/O chip for support of legacy devices such as serial, IR, and parallel ports and the floppy drive.

VIA Modular Architecture Platforms (V-MAP) for Pentium 4

VIA's North and South Bridge chips for the Pentium 4 support VIA's Modular Architecture Platforms (V-MAP) designs, which enable motherboard designers to convert quickly to more advanced versions of a chipset because of a common pinout.

The North Bridge chips used in the P4X266, 266A, 266E, P4M266, and P4X400 chipsets are all pin-compatible with each other, as are the 8233/8235-series South Bridge chips. Thus, motherboards using these chipsets can be built in a variety of configurations. All these chipsets also support VIA's V-Link high-speed connection between the North and South Bridge chips.

VIA Apollo P4X266 Family

The VIA Apollo P4X266 is its first chipset for the Pentium 4 and Celeron 4 processors, supporting AGP 4x, 4GB of RAM, and the 400MHz system bus used by early Pentium 4/Celeron 4 processors.

The P4X266A improves the memory interface and queues more instructions (up to 12) in the processor bus interface to reduce latency and improve performance. The P4X266E adds support for the 533MHz bus used in the 2.53GHz (and faster) Pentium 4 processors. It also supports both the VT8233 and newer VT8235 series of South Bridge chips.

ProSavage P4M266

The VIA ProSavage P4M266 integrates the S3 Graphics ProSavage8 2D/3D graphics accelerators with the features of the P4X266 chipset. Unlike some other chipsets with integrated graphics, the P4M266 retains an AGP 4x slot, so users can upgrade to faster AGP 4x graphics in the future.

The ProSavage8 core uses 32MB of system RAM for its frame buffer, supports AGP 8x bandwidth internally with 128-bit data paths, and features DVD DXVA Motion Compensation to improve the quality of DVD playback. In addition, it supports all members of the 8233/8235 family of South Bridge chips.

Apollo P4X400 and P4X400A

The VIA Apollo P4X400 chipset is an improved version of the short-lived P4X333. It's suitable for both server and workstation/desktop computer use, thanks to its support for up to 32GB of RAM and ECC memory. It also supports 400MHz and 533MHz system bus speeds and DDR memory up to 333MHz.

It uses the VT8235 South Bridge, so it also supports the latest I/O standards (USB 2.0 and ATA-133). The P4X400A chipset features improved timings and support for DDR400 memory and uses the VT8235 South Bridge.