Hi, give the comp some work to do. I think you're seeing amd cool and quiet kicking into action, it drops the speed and voltage when near idle to save power and heat (no heat, no fans)!
Being on line probably uses 5% of the 800mhz of your cpu. So your processor is in power save mode.
Download Prime 95 and start it. Your processor will jump to 1.8 ghz. Turn off prime 95 and your processor will return to 800mhz.
Your processor slows itself down and lowers the voltage to save power and produce less heat.