its NOT because its set to auto.
do you even know what Auto means?
Auto means that it automaticly uses the best possible agp speed which would be 8x since your card can do 8x.

raven shield is known for its sucky performance.
but what game settings are you using?
maybe your just going over your hardware limit??
and you can check in your control panel for your gfx card what agp speed you are running at.

but FORGET about the auto thing because its not the cause.
i KNOW since i had an kt4 board and had my agp on auto :P