Can one rig run multiple different graphics cards? I have some 7950 and some R280, can I connect them both on one rig? Will it work normally? Or does system require all GPUs to be same?
Nope, you're good to go. You don't even have to connect them all through PCI-e. With cgminer, you can set the settings uniquely for each card. You can use any kind of adapter that would normally bottleneck GPU performance.