Crossfire on P965 Preview

ATI just released drivers enabling Crossfire support on the P965 chipset for DX games and the first benchmarks are in:

http://www.anandtech.com/video/showdoc.aspx?i=2837

This is on an ASUS motherboard using a beta "performance-enhanced" BIOS. They tested using an X1900XT Crossfire setup and found that the performance is about 3-9% lower than on the i975X. This is understandable considering the x16/x4 setup and the fact that data is travelling between the NB and SB through the DMI interface which was never designed to handle that type of traffic. Both ASUS and ATI are continuing to tweak, but it'll never quite reach i975X levels. My feeling is that Crossfire will work as follows:

2 x X1300 - Should run at full speed (ie same as i975X) for all varieties.
2 x X1600 - Should run at full speed for all varieties.
2 x X1800GTO - While PCIe x4 provides enough bandwidth for a single card, the additional Crossfire traffic will likely result in slightly reduced performance.
X1800GTO/XL + Master Card - Full speed.X1800XT + Master - PCIe x4 slightly bottlenecking card, but Crossfire traffic over dedicated connector should mean difference isn't great.
2 x X1900GT - Insufficient bandwidth for both card and Crossfire traffic, noticeable performance decrease.
X1900GT + Master - PCIe x4 slightly bottlenecks card.
X1900XT/X1900XTX/1950XTX + Master - PCIe x4 bottlenecks card.

2 x RV560 - PCIe x4 sufficient for single card and dedicated internal Crossfire link means should run at full speed.
2 x RV570 - PCIe x4 slightly bottlenecks single card, but dedicated internal Crossfire link means should run at near full speed.

Since the whole point in adding Crossfire support to the P965 was to develop a target market for the new mainstream RV560 and RV570 Crossfire (nVidia SLI is too dominant in AMD market and i975X users would likely opt for higher-end solutions), it should workout alright once all the driver and BIOS tweaks are done.

I wonder if ATI enabled Crossfire for the G965 since there are boards that have 2 x16 slots signaled as x16/x4 like the P965.

http://www.asus.com/products4.aspx [...] =11&l3=332