I've been looking for days for the answer to this problem, but none seems to give me the right answer.
AMD Phenom 9600 Black Edition @ Stock
DDR2 Ram 4 GB 800 MHz CAS 5
ATI HD 3870X2 GDDR3 1024 MB
HDD 1 TB (500x2) RAID 0
ZEROtherm Nirvana 120MM
NZXT PP 800W
Vista X64 with Catalyst 8.10
Get to the point
I have a HD 3870 X2 that I bought.. probably half a year ago. It works great with COD 4 1650x1080 with all "eye candy" turn on. I don't have FRAPS at that time, but the frame rates are good enough for me to play with out lags.
But when I install crysis and FSX there seems to be some thing "odd" about this
Using rivatuner and CCC monituring the GPU usage during games, it seems that in crysis what ever resolution I play the frame rates are almost identical (less than 20 FPS)
During benchmark with low settings at 800x600 it gives me 15 FPS average and the GPU usage is about 20-40%
I also tried using high settings at 1650x1050 it gives me 15 FPS average too. But the GPU usage is now around 40-60%
In both settings it seems that the fan doesn't speed up more than 25% and temps never hit more than 65 C
In FSX at 1650x1080 the GPU usage is also around 20-30% giving me around 10-50 FPS depending on the location. The fan seems to spin up faster than usual I would say about 35%.
After going through count less numbers of forums, it seems that people have been suffering powerplay issues with the 38XX series card going back to low
3D mode (300 MHz core clock) during game play, but the odd thing is, even though the other 38XX cards seems to switch back to 300 MHz core clock, but the GPU usage are normally at 98-100%
My HD 3870 X2's clock stays at 825 MHz all the time during crysis and FSX, but the GPU usage going anywhere near 100% it stays 40-50% during crysis and 20-40% during FSX.
As far as i know crysis didnt suport crossfire on release. Dont know where they are with patching it but the 1.1 patch didnt seem to make much differance according to reviews i just googled. Now this would make sence if your card is running 45-50 % thats one core going nearly flat out.
Dont know alot about FSX but i do know that flight sims in general are very CPU centric and dont lean on the GPU that hard. So if it also isnt suporting Crossfire then it would seem about right to me.
Just to say im making the assumption that this is the way the card would be reporting its usage. I dont own one and dont know if it reports total usage or both cores seperatly as a CPU would.