Turning off Sideband Addressing

[RamaAuran]

In a last ditch effort to improve the choppiness and stuttering in my gameplay with my 6800GT, I have been reading over some of the threads and it seems turing off Sideband Addressing helps performance. Unfortunately, I cannot seem to find the option to turn it off in my bios (ASUS P4P800 Deluxe mobo). In using Riva Tuner, it shows as being on, but the option is greyed out to turn it off. Is there another way to turn it off? Thanks for the help.