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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  • Jii - Monday, January 17, 2005 - link

    VT8251 has support for PCI-e, but not for 10/100/1000 LAN?

    There must be an error on the southbridge chip comparison table - at least I hope so.
  • quanta - Wednesday, November 3, 2004 - link

    #7, it is possible count PCIE device as PCI. After all, PCIE software is supposed to be software compatible with PCI.
  • Fluff - Wednesday, October 20, 2004 - link

    Give us RAID-5 dammit.
  • Regs - Wednesday, October 20, 2004 - link

    I believe the VT8251 has 7 because of SLI. 2 slots that could be programmed to 8x PCI-Express. The remaining 5 are normal.
  • JarredWalton - Tuesday, October 19, 2004 - link

    Pete, I must admit that I sort of wondered the same thing. With PCIe being the future and most people currently using at most three PCI boards, adding yet another PCI slot seems pointless. It may have something to do with the integrated PCI devices counting against that total. Just a guess. I doubt that we'll actually see any 7 slot PCI boards ship, regardless.
  • Pete84 - Monday, October 18, 2004 - link

    Any idea why the VT8251 has 7 PCI slot support? What board would use so many? With even three or four add in cars, the bandwidth would be so low it wouldn't be funny . . . so why??
  • TrogdorJW - Monday, October 18, 2004 - link

    #4 - I mention the overclocking not because some of the K8T800 Pro motherboards can't overclock - i.e. the Asus - but because we have had a few more issues getting reasonable overclocks out of the VIA chipset boards. Anyway, the NF3 250Gb still comes with better Gigabit Ethernet, as well as a hardware firewall. All things being equal, I still prefer that chipset. It's close, so if the K8T800 Pro comes with a less expensive motherboard (from a brand you trust), more power to you. We won't know for sure until boards ship, but we like to hope that the PCI/AGP lock will now function properly on all future VIA chipsets. :)

    5 - Typical time from sampling to first availability tends to be around 3 months, I would say. If the new chips are pin compatible, it can sometimes be less. With the new chipsets offering PCI Express, I would guess 3 or 4 months is more likely from most manufacturers, but I'm sure we'll see some before the end of 2004.
  • Noli - Sunday, October 17, 2004 - link

    When it says that the k8t890 and k8t890 pro are sampling now, does that mean anyone can work out when we will actually be able to buy motherboards with these chipsets on them?
  • thebluesgnr - Sunday, October 17, 2004 - link

    "Performance between the K8T800 Pro and Nforce3 250 Ultra is very close, but NVIDIA offers additional features and improved overclocking."

    The overclocking potential for both are pretty much the same. On AT's motherboard roundup for socket 939 the ASUS A8V overclocked just as good as the best nForce3 Ultra mobo. And although VIA K8T800 Pro had problems with its PCI/AGP lock at first, the issues are all fixed now while some nVidia boards are still having PCI/AGP lock issues.
  • xsilver - Saturday, October 16, 2004 - link

    what hasn't been mentioned is if the pci/agp lock will be fully functional on the k8t890pro or have I been under a rock for a while?

    Still I can't see why you would want to buy this over a nforce 4 (NOT a fanboy, they just have such a good track record)
    If the k8t890pro hits with 2x PCI express lanes nvidia surely much hit back with just as much if not more?

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