PT894 and PT894 Pro Chipsets
While the PT880 Pro chipset competes in a class all its own, VIA’s answer to the Intel 915 and 925 chipsets lies in the PT894 and 894 Pro respectively.
Once again, these two northbridge chips support all the features we mentioned on the second page of the article, including both DDR and DDR2 support. Where they differ from the PT880 Pro is that neither offers any support for the legacy AGP bus. Your options are limited to the single x16 PCIe slot on the PT894 or a set of PCIe slots on the PT894 Pro.
This diagram shows the PT894 Pro
The only difference between the PT894 and the PT894 Pro is the additional PCI Express graphics card slot on the design. The second PCIe slot is running at x4 lanes of PCI Express and the primary slot still runs at x16.
Again, as VIA is marketing this multi-GPU setup for multi-display purposes, there is nothing yet on any kind of SLI adherence.
PT894 Pro Reference board
You can see that this board is also a co-layout board, meaning it has both DDR and DDR2 support.