After a very long wait, it’s finally here - the first PCI Express chipset for the Athlon 64 platform. Unsurprisingly, it comes from VIA, although chipsets are expected to follow from nVidia, SiS and ULi. The K8T890 supports AMD’s full range of processors from the Opteron server chips, the FX and Athlon 64s as well as the new Socket 754 Sempron.
The K8T890 is the first in a new family of chipsets from VIA and adds some new functionality apart from PCI Express. But let’s concentrate on this first, since VIA has taken a different route to Intel, with what it calls Flex Express architecture - the K8T890 chipset offers one x16 slot for graphics cards as well as four x1 slots for peripherals, all connected to the Northbridge. Intel on the other hand only has the x16 slot connected via its MCH (equivalent to the VIA Northbridge) while the x1 slots are connected to the ICH, which in turn is connected to the MCH by a 2GB/sec link.
So why is this important you might ask yourself? Well, as each x1 PCI Express lane is capable of 500MB/sec, the way that Intel has implemented PCI Express means that there is still a bottle neck in the system via the chipset interconnect bus, something that VIA has overcome with the Flex Express architecture.
Then consider that your PCI, SATA, IDE, USB and FireWire devices will share the bandwidth with the PCI Express slots in an Intel system and it’s easy to see why VIA has taken a different approach to its PCI Express implementation.
Since the K8T890 is an Athlon 64 platform there is no support for DDR2 memory - Athlon 64 processors don’t support DDR2 memory as yet and only AMD can tell us when this will happen. This means that if you already have a system with expensive DDR memory, you can use it with the K8T890 chipset. What you don’t get is an AGP slot, as it seems that VIA has decided not to deliver a chipset that supports both AGP and PCI Express, at least on the AMD platform.
Sadly, VIA’s new Southbridge, the 8251 will not be available at the launch of the K8T890 chipset, which means that motherboard manufacturers will have to use the older 8237. The new Soutbridge will add a further two PCI Express x1 slots and is compatible with older VIA chipsets. Further more it adds support for SATA native command queuing, High Definition audio, improved V-RAID and support for four SATA drives.
Later this year VIA will release the K8T890 Pro, which adds support for what VIA calls DualGFX Express. This is VIA’s implementation of SLi support, but it doesn’t give you two x16 interfaces, but rather one x16 and one x4 with an x16 slot. This should however not affect the performance of SLi graphics cards from nVidia since its implementation doesn’t send any data over the second PCI Express interface. This also means that you don’t get any extra slots for peripherals on the motherboard unless it is teamed up with the new 8251 Southbridge.