I have a Gigabyte HD 7970 (GV-R797OC-3GD) installed in an Asrock X79 Extreme6. The card works great once the OS driver has loaded (ie, I've never had the problem once I get into Windows 7) in both 2D and 3D modes. However, from POST until the OS driver loads, I get strange intermittent flickering. Sometimes it is so bad that I can't read what's displayed on the screen. This makes navigating the UEFI bios, etc, quite difficult/impossible. Yet it doesn't happen all the time.

It kind of looks like there is some sort of incompatibility between the bios-level video driver and the HD 7970 that makes it difficult for the monitor to detect the video signal. When I swap an older HD 4850 in the same slot, same monitor, same cables, the issue has not occurred.

This has occurred with both 1.1 and 1.2 bios versions for the Extreme6.

Any ideas?