just to let you know 4 cards run fine on 4gb ram on windows 8.1 but 5-6 cards need 8gb...
at least for me;)
I've been running 5 290s on some of my rigs with 4GB ram with no real problems, so i'm not entirely sure that's true. It's got more to do with available virtual memory, i surmise.
Perhaps Claymore can comment on physical ram requirements, i would be curious to know.
I cannot find exact requirements. In most configurations it works with 4GB RAM with any number of cards. But sometimes 4GB is not enough. Virtual memory definitely helps, but if you have only 2GB of RAM it won't work in most configurations anyway. It is something related to AMD drivers and I cannot find any public documents about it.