i'll try and give the 7990's a shot and see what happens. can you tell me some OpelCL app under windows which i can use to stress all the gpus?
I think stressing is not necessary. If clinfo gives you all the devices and you can do a simple vector addition on each of them, they will work under load too. I have never noticed any difference between 0.01% load and 100% load in terms of driver behavior. But if you really want, you can either google one (can't be so difficult as when I was looking for linux-based stress tests they were all windows-only) or you can try folding@home, bitcoin mining or other similar projects.
2 Radeon 7990's with 4 Tahiti GPU's working like a charm on windows 7 64bit with luxmark
platform intel x79 core i7 3930k processor
i don't believe powercolor has official 7990's... that could be your issue.
or it could be a driver thing, the ones that i am testing are meant for this card.
I hope AMD see, that more and more people want to do something like this and start to do something.
W10000 seems to be a Dual Tahiti FirePro card
its actually S10000 and yes these are official dual tahiti firepro cards unlike what the op has
and in my post below the '7990' i was used for testing were actually the s10000 cards