I've owned a 4870 1GB from Powercolor up until now as I've just recently purchased a Sapphire 4870 1GB and plan to put them in CrossFire.
Here's a basic timeline of what happened:
-Installed the GPU, 2 CrossFire bridges used to connect cards.
-Let Vista 64-bit install the card
-Noticed card isn't able to be CrossFire'd in CCC <it was greyed out>
-Checked bridges and turned out I hadn't plugged them properly on.
-Plugged them in properly; option still greyed out.
-Used the install disc attached to install the drivers, etc.
-CCC now allowed the Enable CrossFireX box to be ticked but it wouldn't stay that way, it would simply disregard me pressing Apply and Ok.
-Downloaded CCC 9.6 & drivers that accompany it.
<<Now it get's wierd>>
-CrossFireX is able to be enabled and so I enable it and it stays, etc, all seems good.
-Do the Crysis Benchmark; no increase in performance.
-Check GPU usage via Rivatuner's Hardware Monitoring feature whilst playing Crysis, FSX, Wings Over Europe, UT3, the second GPU doesn't do anything
GPU-Z, etc says the CrossFire is working <well actually it says its working but unsure for Vista 64 bit> but the card doesn't actually contribute to anything other than increasing temperatures from 54 to 80C on the original card.
Tried one bridge, no difference at all, looked through my BIOS, couldn't find anything that conflicted <As far as I know, if you have a suggestion PLEASE speak it>.
Tried re-doing the drivers, I'm at my wit's end.