4x 6870 Windows 7 Miner Crash

[Reno]

Hi there,

got some issues with my new Rig.

Got 4x 6870 running on Windows 7 64 bit.
I can mine with 3 cards without any problems, as soon as i plug in the dummy plug for the 4th card the miner won't start anymore, just crashes instant (tried: Phoenix Miner, Phoenix Rising, GUIMiner).
Got a 1200w high quality PSU (Silverstone) with a lot of ampere etc. Mainboard is a MSI 890FXA-GD70.
I tried to connect 2 cards with a crossfire cable and put the dummy plugs into the 2 other cards.
This is working, but i can't adjust the core clocks, memory etc. and the crossfire mining performance is about 15% lower.

I remember some older thread with the same problem but i can't manage to find it anymore

MSI Afterburner won't start either "Unable to initialize display driver wrapper".

Any suggestions? I can switch to a linux distribution too if this will help.

Edit: Tried 11.6 and 11.5 both with sdk 2.4

[padrino]

I had 6 GPUs working in Windows 7 with 11.6, couldn't get it working with anything but that but when it was MSI afterburner couldn't hang. I moved to Linux and I can run 8 stable, I gave up fighting Windows.

[Reno]

Same Problems running Windows XP 32 bit.

Any suggestions? :/