Anything over 4GB or Ram disables my Graphics Card

[co319]

I have an asus P5QC mobo with Vista 64bit as OS, I bought 4 2GB ocz pc6400 800mhz ram for it, it works great with 4gb, but if I add an additional stick or two, it automatically disables my video card.

Video card is a ati radeon x850 xt platinum edition with the latest catayst for vista 64. Ive tried upping the ram voltage, cpu voltage, uninstalling and reinstalling drivers but nothing seems to work. It will only work with 4gb total but I want to run the full 8gb since I bought it already. Any ideas?

 

[GhislainG]

Is memory remap enabled in the BIOS?

 

[co319]

Yes, It's eneabled. If I disable it, then It will work, but it runs very slow and the graphics will display in slow motion. The mobo manual says to keep it enabled for 64 bit os.

 

[GhislainG]

Have you tried using another video card to see if it resolves the issue? For testing purposes, you could even use an old PCI card. If the video card is the source of your problem, then you'll have to replace it.