I'm posting to see if anyone is having better luck with Crossfire, specifically with a pair of 6950s. I'm starting to have sporadic display issues and cannot get the cards to run at 8x/8x using PCIE2 and PCIE4 (the two 16x lanes on the board). When the display does work, whichever card is in PCIE2 seems to only run at 4x.

After completing the build in July, I had no problems like the one described above. Both GPUs worked in crossfire just fine. I discovered this issue after returning home from vacation. The machine was on while I was gone and I have no indication there was a power surge or outage.


System Specs:
i5 2500k @ stock | ASRock p67 Extreme4 (B3) UEFI 2.0 | 2x4GB G.Skill RipJaws X PC3 1600 | 2x MSI R6950 Twin Frozr III 2GB @ stock | OCZ ZX 850w 80+ Gold | OCZ Agility 3 128GB SSD | Win7 x64



Symptoms:
Sporadically, my monitor will remain in power saving mode - indicating no signal from the GPU
This occurs most frequently after a soft restart (from Win7), but also on a cold boot
The display is blank at POST and stays blank during Windows boot sequence
The fans on both GPUs continue to run
Using RDP, I can connect to the machine and login to Windows. Catalyst Control Center is not available in RDP. GPUz works normally.


The issue occurs sporadically - meaning:
I can sometimes restart the machine from Win7 with no problems - both cards run at x4/x8
I can sometimes shut down the machine via Win7, then power it back on and boot into Win7 with no problems - both cards run at x4/x8


Temporary Workarounds:
I can sometimes resolve the blank display issue by shutting down the machine completely, waiting a few seconds and powering it back on.
This does not resolve the bandwidth link speed issue, just the display.


In Crossfire:
I can replicate this issue with both R6950 cards, regardless of which one of the GPUs is seated in PCIE2
If I swap the DVI cable to the GPU in PCIE4, the display works fine. After a reboot, the card in PCIE2 is not detected.


With a single 6950:
I can replicate this issue with a single 6950 in PCIE2, regardless of which one of the two GPUs I use
When the display does work, each GPU registers as running at x16 in GPUz
When either GPU is placed in PCIE4, it boots normally and the display works normally. GPUz registers the card at 8x


Hardware Troubleshooting:
Confirmed monitor works normally when connected to another PC via the same DVI or DVI-DSUB cable
Confirmed secure power connections to motherboard, GPUs and drives - 4 pin molex plugged into CF/SLI port on motherboard
Confirmed that both cards were seated properly in the PCIE slots
Confirmed that both cards were in the proper PCIE slots to take advantage of 16x lanes (PCIE2 and PCIE4 per manual)
Confirmed both RAM sticks are properly seated
RAM passes Windows Memory Diagnostic without issue


UEFI:
I can replicate this issue using UEFI (bios) versions 1.60, 2.0 and 2.10
I can replicate this issue after clearing CMOS and loading UEFI (bios) defaults
I can replicate this issue with the following devices disabled in the UEFI:
Onboard HD Audio
Serial Port
Floppy Controller
1394
Marvell Sata 3.0 controller


Other UEFI settings:
Primary Boot device is OCZ Agility 3 SSD on port Sata3_0
Sata Mode is set to IDE Mode, Sata Controller 0 is set to compatible, Sata Controller 1 is enabled


Drivers Installed:
Intel INF (provided on ASRock CD) ver 9.2.0.1015
Catalyst 11.9

I can replicate this issue after a clean install of Windows 7 x64 SP1

Any advice or suggestions that anyone can provide would be most helpful. As far as I can tell, I either have something configured incorrectly in the UEFI, or I have a defective piece of hardware. Given that both GPUs work fine in PCIE4, I'm not convinced it is one of them. Given that I can RDP into Windows while the display is blank, I'm also inclined to think that the PSU is fine. Most likely, I have a conflict in the UEFI that I need to resolve, or I have a bad motherboard. I've got a ticket in to ASRock Support as of 10/22 and I'm awaiting a response.

Thanks!