I have the asus p5q pro motherboard, which only supports Crossfire in x8 PSIe2.0 mode. I was going to buy a whole new CPU/MB/RAM, but I already have a Q9400 with 4gb DDR2 1200 ram, so I'm going to upgrade graphics only, as my GTX260 is the likely bottleneck in BF3.
So my options are:
single Nvidia or AMD graphics card, probably GTX570 is best bang for buck?
Or, what I had in mind to squeeze more framerates out of a smaller budget, two XFX AMD Radeon 6850 1GB cards in CrossFire, running at x8 in the current motherboard.
Objective is obviously to play BF3 at 1920x1200 at highest possible settings and obtain 50+ minimum FPS. I have a 750W Antec power supply, ample cooling and $350 maximum budget. The two 6850's go for $330 before a $60 mail-in-rebate, plus I get a free $49 game.
1- There's no significant difference between X8, X16 CF a slight crease in performance by 5% between the X8, X16 configurations. so no issue from going X8, X8.
2- I saw your MOBOs specs it mentioned CF only no SLi, download the manual and double check that.
3- A single GTX 570 or HD 6970 will max out BF3.
4- Running HD 6850s in CF is not a good idea because of Microstuttering explained recently by Tomshardware, the problem is not noticeable while running strong GPUs such as HD 6950s
5- Upgrade your CPU or get it overclocked to the max in order to game without performnce lag.