I've read the 5870 BIOS works wonders on the 5850...
BIOS collection -
Only if you have a reference cardTemp difference is normal with the multi-card GPUs I've had in the past. Device0 assumes a 'master' role while device1 (device2, etc) become slaves and take a large load off the master card, typically running a bit cooler and a bit less than the master card.
I don't understand the fluctuating activity, tho.
"Facts do not cease to exist because they are ignored." -A.Huxley