VIA Socket 478/775 North Bridges

VIA has Pentium 4 chipsets both with and without integrated graphics. Features vary a little, with the discreet parts generally being more performance/enthusiast oriented. Here is the list of current and upcoming discreet chipsets.

Platform Summary - Discrete P4 Chipsets
PT880 Pro PT894 PT894 Pro
Processor Bus 533/800/1066MHz 533/800/1066MHz 533/800/1066MHz
Memory Support Dual Channel DDR-1 333/400 & DDR-2 400/533/667 Dual Channel DDR-1 333/400 & DDR-2 400/533/667 Dual Channel DDR-1 333/400 & DDR-2 400/533/667
Graphics Support Universal Graphics Interface: PCI Express and AGP 3.0 PCI Express VIA DualGFX Express (Dual PCI Express)
Chip Interconnect Ultra V-Link Ultra V-Link Ultra V-Link
South Bridge VT8237 VT8237/VT8251 VT8251
Sampling Oct. '04 Now (Sept. '04) Oct. '04

As you can see, all of the designs are very similar in terms of features. The key difference is in their south bridge and graphics support. First, let's talk about the graphics. The PT880 Pro will be one of the few options for motherboard manufacturers looking to include fully functional PCI Express and AGP graphics interfaces. We have heard of a bridged PCI-to-AGP connection being offered by some manufacturers, but the VIA chipset should provide full AGP compatibility without a bridge. This may be the only real performance option for those looking to migrate gradually from AGP to PCI Express.

On the high end, dual PCIe graphics interfaces will be an option with the PT894 Pro chipset - each will run as a PCIe X8 connection, but they will be X16 slots. As we have yet to tap the full potential of AGP 8X bandwidths, this should not present a problem. As far as the South Bridge features, we'll cover that in more detail in a moment, but the PT880 Pro is limited to the VT8527 South Bridge while the PT894 Pro is requires the VT8251 South Bridge, and the PT894 can support either one. The VT8251 is a more advanced - and expensive - option, so the PT894 Pro will be targeting the enthusiast market.

You can also see that, similar to Intel's i915P chipset, all of the VIA chipsets will allow for the use of either DDR or DDR2 memory; although the use is exclusive so you will not be able to use both DDR and DDR2 at the same time. VIA also offers the PT800 and PT880 - and several other older chipsets. They are more or less like the PT880 without PCI Express or DDR2 support, and the PT800 features a slower chipset interconnect. VIA uses their proprietary V-Link design for the chipset interconnect on all of their current chipsets. The link runs at 533 MHz and uses either an 8-bit (8X V-Link) or 16-bit (Ultra V-Link) bus. This provides for 533 MB/s or 1066 MB/s of bandwidth, respectively, which is more than enough for the current demands of South Bridge devices.

Platform Summary - Integrated P4 Chipsets
P4M800 P4M800 Pro PM880 PM890
Processor Bus 400/533/800MHz 400/533/800MHz 400/533/800MHz 400/533/800MHz
Memory Support Dual Channel DDR-1 333/400 & DDR-2 400/533/667 Dual Channel DDR-1 333/400 & DDR-2 400/533/667 Dual Channel DDR-1 333/400 & DDR-2 400/533/667 Dual Channel DDR-1 333/400 & DDR-2 400/533/667
Internal Graphics UniChrome 200 MHz UniChrome Pro 200 MHz UniChrome Pro 250 MHz DeltaChrome IGP (DX9)
External Graphics AGP 4X/8X AGP 4X/8X AGP 4X/8X PCI Express
Chip Interconnect 8X V-Link 8X V-Link Ultra V-Link Ultra V-Link
South Bridge VT8237 VT8237 VT8237/VT8251 VT8251
Sampling Now Nov. '04 Already Available Q1'05

Moving on to the Integrated Graphics chipsets, we have four options. The PM800 and PM880 are already available and only provide support for DDR RAM, with the PM880 offering a faster interconnect and support for the VT8251 South Bridge. They both feature S3 UniChrome Pro integrated graphics, although there may be a difference in the clock speed of the IGP. The only additional feature of the PM800 Pro appears to be DDR2 400/533 support; the additional bandwidth that DDR2-533 offers should improve the performance of the IGP somewhat. At the top of the IGP chipsets we have the PM890. It uses the DX9 capable DeltaChrome IGP and provides support for an add-in PCIe graphics card as well as DDR2-400/533/667 memory. As with the PT894 Pro, it only supports the more advanced South Bridge and will geared more towards the enthusiasts. Performance of the DeltaChrome IGP is not likely to come anywhere near the level of a discreet NVIDIA or ATI graphics card, but it should compare favorably with the Intel GMA900. Driver support for the integrated graphics is always a big concern, and we can only hope that it will be better than what we have seen in the past.

Index VIA Chipsets for socket 754/939/940


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