11-16-2013, 07:08 AM
You won't be able to have more than 4 hd7990 (8 gpus) on a single rig. If you can watercool and have a good leakproof loop, it's going to be a great cracking rig. You will have to test it yourself to know how much you can overclock. I am not sure that it's going to be that much since they will probably generate a good amount of heat. I have read somewhere that you need 1 rad per apparatus you want to cool but in these days, double GPU cards did not exist as far as I know. Good luck with your build.