The KT400 chipset
As this is our first look at the KT400 chipset, I'll take a moment to see just what it adds over and above the successful KT333 chipset and previous front-runner, the KT266A.
On first glance it appears that not a whole lot has changed in the transition between chipsets. The first notable 'upgrade' comes in the form of support for AGP 8x. The SiS Xabre and ATi's Radeon 9700 both support this new AGP graphics transfer speed. The bandwidth is doubled from the present 1.05GB/s to 2.1 GB/s between Northbridge and AGP port. Although this sounds impressive on paper, numerous tests have shown that present-day graphics cards can barely saturate the 1GB/s on offer presently, much less satisfy the 2GB/s that AGP 8x affords you. Having said that, future graphics cards will tax this increased limit. I tend to see this as a forward-looking measure.
The link between the two VIA bridges has been increased to 533MB/s, although this is present in the newer revisions of the KT333 chipset. We now see 6 USB2.0 port integrated into the VT8235A Southbridge. Again, this is present on some of the newer KT333 'boards.
There's still no integrated inclusion for Firewire (1394s) support that we've seen on a few Pentium 4 motherboards. Neither is there any mention of in-built support for Serial ATA, the much-vaunted replacement for current IDE drives.
In short summary, we have direct support for DDR333 memory, unofficial support for DDR400 memory. An upgraded AGP transfer speed and a faster link to a South bridge that now accommodates 6 USB2.0 ports via the use of 3 controllers, ATA133 hard drive standard, and on-board Ethernet.