I was having many issues with AMD Catalyst control center, freezing, artifacts, etc., so I just deleted it, and I believe, am currently using Windows display drivers (Win7) with the HD6990.
This has worked all right mostly, but I'm wondering if it's disadvantageous to do? I've had a few blue screens relating to the graphics card (one while gaming, one while using regular applications), so I'm wondering if this behavior is possibly linked to my lack of AMD specific drivers.
Overall, I've found the system (I run 4 monitors, which apparently, even though the card supports it, seems to tax the capabilities a lot even when just running basic office apps; I get blurring when I move windows, occasional hiccups with windows flickering, and some other weird behaviors) I would argue the multimonitor driver support is still very buggy.
So... Question being: AMD drivers or Windows drivers?
sounds like to me that you installed a gpu into a pre built system and forgot to use a larger power supply and the power supply that in the pc is maxed out so under load the video card not getting the good clean power it needs. and the lock up and crazy images are showing up. if your mb has onboard video ipgpu try turning it on and using it to drive one or two monitors. and se if the 6990 runs better. if you do have a large power supply in your pc. make sure your mb chipset drivers are up todate. also use gpu-z make sure the pci bus is reading the gpu right. last things i would check are mb bios updates and use cpu-z see that your mb set your ram to the right speed and timing.
Use the AMD drivers, the Windows drivers are a minimal set meant to get you going. Since you have uninstalled the Catalyst drivers, make certain they are completely gone from your system then download the latest drivers from here -> http://support.amd.com/us/gpudownload/Pages/index.aspx
I'm running 4 monitors (3x30'' and a 24'' all at max resolution) off a single AMD HD6990 card (with adapters for mDP on 2 of them unfortunately).
Everything runs fairly well, but I experience some 'blurring/dragging' effects when I move windows around the screen. That is, when the edge of the window box moves, it will ghost/fragment a small amount before the monitor 'redraws it.'
It's not a performance problem, just vaguely annoying - and I'm wondering if it's a problem relating to the card, the number of monitors running, or the drivers.
The drivers are the newest possible now, thanks to some forum help here, though that didn't correct this particular issue.