I'm having some strange issues with my 4870x2 ever since the 10.1 drivers came out. I've gone back and forth between the 9.12 drivers and various 10.X drivers, but the issues persist now. In order to correct the issue, I actually have to rebuild the OS.
First off, my performance dropped off dramatically. My system actually performs better with my original 4870 (512MB card) than with the 4870x2 in just about everything. The only thing I've been able to run better witht he dual gpu card is Doom3. Granted, I don't run majorly complex games. I run World of Warcraft, Diablo 2, Doom 3, Unreal Gold, Rise of Nations and Starfleet Command. With most of these games, they run fast enough that I don't even notice the difference. The only noticeable differences are in Doom3 and WoW.
However, the differences in WoW are dramatic. In non-crowded parts of the game, the performance isn't much of a problem with either card, but that's not where I spend most of the game. In a crowded Dalaran, where most of the players hang out right now, the 4870 gives me 4XAA at about 40fps. the 4870X2 gives me about 15fps. In dungeons, when there are lots of spell effects going off, and proper performance is vital, the 4870 will give me a pretty consistent 60fps, but the 4870x2 will sometimes skip down to about 5fps, seemingly at random. I'll go through half a fight at 60fps, then suddenly my fps will drop to the floor and run at 5fps, then it comes back moments later, after we wipe. This is very frustrating. Specifically because of this, I have gone to the 4870 full time, relegating the more expensive card to sitting in an antistatic bag on my desk.
Doom3 isn't so much of a problem. It just consistently runs about 15% slower on the 4870x2 than the 4870.
Benchmarks are also showing up oddly. the Sisoft Sandra GPGPU test shows the 4870x2 about 15% slower than the 4870. 3DMark06 consistently runs about the same.
I also totally rebuilt my system in February with a new motherboard, processor, (Core i7 920, currently overclocked to 3.5GHz) and hard drive (OCZ Vertex 120GB, moving my Apex 60GB down to a secondary role holding temp files and some of the older programs, with a 4X 750GB Caviar Black RAID10 for storage.) Even with the rebuild, and only installing the 9.12 drivers, these problems persist.
Anyone have any suggestions on this? Anyone else see anything like this?
Have you considered the card has experienced hardware failure ?
Check what gpu-z gives you for information.
When just the 4870x2 is installed, did you try disabling crossfire in ccc, to see if you had 'ok' single gpu performance then ?
One member had a weird failure with a 4870x2 where communication between the two gpu's dropped to 4x, or some similar oddity. The card then gave poor performance, where it had operated fast/correctly before.
I have confirmed it: one of the GPUs is simply not being recognized at all. I'm guessing this is messing up the performance of the one that is working, giving me even slower performance compared to a single 4870.
I decided to go ahead and get a GTX 470 to replace it. I'll get a second one later, when I can afford it. (I have 4 car payments left and then I'll have an extra $500 a month in disposable income.) Now I have a whole bunch of new issues with the GTX 470, but I'll post those in the nvidia forum.