VIA's K8T890 AMD PCI Express platform

Southbridge Faceoff

Comparing VIA's VT8251 southbridge to Intel's ICH6, both offer 8 channel high definition 192Khz/24bit audio, Intel labeling theirs 'Azalia' and VIA 'Vinyl Audio'. VIA supports an extra ATA133 port over Intel’s ICH6 - this will make it easy for users of multiple IDE devices to upgrade motherboards without switching their storage to SATA at the same, expensive, time.

Two bridges vs one?

AMD's HyperTransport technology is designed to work most efficiently in a single bridge setup, rather than in the classic northbridge/southbridge array. With an extra chip in the equation, the latency when accessing the southbridge from CPU increases because information from the CPU has to pass through the northbridge before it gets referred to the southbridge. In fact, when is a northbridge not a northbridge? According to IBMs 1981 specification of an x86 computer: the term "northbridge" is synonymous with the complex / high speed inter-workings of the memory controller, but since that is now integrated into the CPU, technically the K8T890 isn’t even a northbridge anymore!

So, why has VIA kept the classic two chipset situation and not adopted a single chipset setup? Why annoy engineers with more complicated setups than necessary? The answer is easy - functionality.



At this time the market is in an interim period between AGP and PEG, DDR and DDR2, PCI and PCI-E. Many people are in lots of different potential upgrade situations making the market less defined. Since PCI-E and PEG cards are in their infancy and are not readily available at the moment, upgrading a motherboard is potentially more expensive than usual and will make a lot of people think twice before upgrading, meaning they will hold out with their current systems a little longer. This situation would be undesirable for motherboard and chipset manufacturers, who obviously want enthusiasts to buy, buy, buy.

In order to maximise their sales, VIA are aiming for functionality and flexibility rather than absolute performance in this first generation chipset. We don't know yet that the platform won’t successfully compete with the equivalent NVIDIA or SIS variations in terms of speed, but VIA's main aim appears to be to let the motherboard manufacturers 'mix and match' between old and new, pin compatible chipsets to make the best solutions for the markets their motherboards are targeted at, even mixing AGP and PCI-E solutions to create a hybrid board. The 'Ultra V-Link' between the north and southbridge should be fast enough to prevent bandwidth being an issue, but there will inevitably be a degree of latency to trade-off against the flexibility.

Looking to the future

With the introduction of the K8T890 Pro later this year, we have the introduction of dual PEG x16 slots. The four x1 slots are removed and replaced with the other PEG x16 slot. What kind of boards we will see the K8T890 Pro in however, is yet to be decided - VIA are aiming this at the high end workstation/server combination (Opteron and socket 939) but it may be seen on socket 754 motherboards should manufacturers think it'll sell.

An integrated graphics solution is likely to appear in the flavour of K8M890, with on-chip S3 DeltaChrome DirectX 9.0 graphics and PEG x16 support. This is most likely to be aimed at OEMs.


In all, the K8T890 series should provide an interesting range of motherboards with the possibility of a variety of combinations, so check the details before you buy. Performance is, as usual, expected to be in the top end but wait for comparative reviews as always (watch this space!). Samples have already been sent out to manufacturers this month so expect retail boards to hit the market within the next few weeks and wider circulation hopefully by the end of next month. We will, of course, update you here on bit-tech.net as soon as we get boards.