I have a Sapphire Radeon HD 6850 1GB. It's running on the latest drivers (Catalyst 12.1). When running games, I noticed that sometimes they loaded very quickly, and other times they where much slower to load (same game). At first I thought that it might have been some background process that was slowing things down, so I tried running the game immediately after the system booted up, but got the same thing. I checked the Catalyst control panel and noticed that on the hardware page (under Information), the Maximum Bus Setting was PCI Express x8 (this is when the game was slow to load). I rebooted the system and ran the game again, and this time it ran perfect. I checked the CCC again and it read Maximum Bus Setting x16. It seems that my system is randomly changing from x8 to x16. I checked the CCC several times, immediately after start up, and it was different every time (sometimes x8 and sometimes x16). I tried restoring default settings in the BIOS, updating drivers and disabling advanced power management to the PCI Express, with no effect.
My specs are:
MB: Gigabyte GA-MA790X
CPU: AMD Athlon X2 250
RAM: Kingston 4GB DDR2 800
GPU: Sapphire Radeon HD 6850 1GB.
PSU: Huntkey 650W
OS: Windows 7 Ultimate 64bit
I know that my PSU is crap but I can't afford anything else right now and seeing as it does work properly about 50% of the time, I don't think it's hardware related.