It has to be a driver issue because I see people running 6 and 7 cards, and I'm through trying to figure it out. Everything works fine in windows 8.1 except for my gpu mapping, it's all fucked up so I don't use Win 8. Not dealing with that. Hopefully a driver update from AMD will fix the Code 43 in win 7. I want to call and see if I can speak to someone at AMD who know what's going on, but I don't know if that would get me anywhere. Over to Linux for now.
I would not count on AMD to release drivers for windows 7 that allow you to run 6 cards. It's not going to happen, not straight from AMD. Why would they? There's really no support for gaming cards, that is the reason the firepro series exists and why they cost so much more for so little relative power, all the $$$ is in drivers and support.
If anything, someone will figure out how to modify the drivers. Right now, Linux will do what you want though.
Also, I don't think nvandertill was asking about the USB thumb drive, but the manuf. of the 290 cards themselves.
Quit jacking with BAMT and go straight to Saucy Salamander!