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PCI Express dips below the equator
VIA's Ultra V-Link interconnect will join the K8T890 north bridge with one of a couple of different south bridge chips. Initially, the K8T890 will be paired up with the VT8237 south bridge, as it was in the prototype motherboard we tested. Soon, though, VIA's new VT8251 will hit the market and quickly become the preferred companion to the KT890 north bridge.


A block diagram of the K8T890 chipset. Source: VIA.

Many of the VT8251's features mirror those of the ICH6 south bridge of the Intel 900-series chipsets. The VT8251 will include two PCI Express lanes, just enough to outfit a motherboard with a pair of PCI-E X1 expansion slots without overwhelming the 1.06GB/s Ultra V-Link interconnect to the north bridge. VIA has added support for Intel's High Definition Audio standard, so the new south bridge will be able to stream eight channels of audio data at resolutions up to 24 bits and sample rates to 192KHz. Also, like the ICH6R, the VT8251 will support the AHCI standard for Serial ATA drives. AHCI includes provisions for hot-plugging devices and the performance-enhancing Native Command Queuing, raising the very real possibility that Serial ATA will kill off SCSI, even in high-end servers.

Because Serial ATA is growing in popularity, VIA has endowed the new south bridge with four ports of SATA connectivity without the need for an external PHY chip. All four of the drives connected to these ports will be able to participate in RAID arrays, with RAID levels 0, 1, 0+1, and JBOD on offer. Two ATA/133 ports remain, as well, for older hard drives and other storage devices.

One of the more interesting decisions VIA made with the VT8251 was to leave out Gigabit Ethernet support and stick with 100Mbps Ethernet. VIA seems to have determined that with PCI Express, Gigabit Ethernet would best be left to an external controller chip. In fact, VIA's press materials on the VT8251 cite higher performance with PCI-E-based GigE than with NVIDIA's integrated GigE solution. I suspect VIA will have success with this approach, because it is likely to please the penny pinchers at Taiwan Inc.'s motherboard manufacturers. By contrast, NVIDIA has pledged to offer more and better hardware acceleration of networking tasks in its future chipsets. I'll be interested to see whether NVIDIA can continue to differentiate its product (and charge more for it) by offering its integrated GigE and firewall.

More north bridges planned
VIA has two more 890-series north bridges in the works for the Athlon 64. The most exciting is probably the K8T890 Pro, equipped with what VIA is calling DualGFX Express. This is VIA's SLI-ready north bridge with support for dual graphics slots. Judging by everything I've seen and heard, I don't believe VIA has worked out yet just how the allocation of PCI Express lanes to each of the two slots will work, but the company does appear to be committed to the idea of building an SLI-capable chipset. The diagram of the DualGFX Express architecture VIA supplied is deliciously vague:


Realistically, I tend to think the vanilla K8T890 north bridge should be able to drive a perfectly acceptable dual PCI-E graphics implementation. Eight lanes of PCI Express per slot should be plenty for a good while yet. I'm curious to see how VIA decides to handle it. They will probably have to match NVIDIA lane for lane on both slots in order to sell their solution. Already, NVIDIA has been informing the world that the next nForce will be the only "certified" SLI chipset for the Athlon 64. That confidence speaks volumes about the openness of the certification process.

VIA's roadmaps say the K8T890 Pro should be sampling right about now, with production coming later this year.

Another K8T890 variant VIA's cooking up is a mobile/value version of the north bridge with integrated graphics. The reasonably decent DeltaChrome graphics technology from S3 will finally find a suitable home in the K8M890. If S3 follows through on its unified driver plans, the K8M890 could be VIA's most competitive integrated graphics chipset in ages. The KTM890 should also arrive some time this year, after it samples in October, if all goes as planned.