Hello all,
Would have initially said check your page file, but it seems to match your 4x4gb @ 16gb.
I'm thinking here is some sort of BIOS limitation - can I ask what CPU you are using? It's not an APU is it?
There is some sort of bottleneck when you are running more than 2 cards - most of those boards are rated for SLI, but it really depends on the board with anything more than that.
I recommend maybe getting a cheap AM3 board with a Piledriver or maybe an FX6300, should run stable.
It's a AMD Phenom X4 9550, MBO is GA-MA790X, I put latet BIOS.
Maybe it is MBO, my thoughts too I but have to ask and check, it's a bit incovinient to buy new MBO, Proc and RAM.
Grub parameter is already there so it's not that.