Running the AGP bus at anything above 66 is potentially bad. Normally it's at 1/1 on a 66mhz fsb, or 2/3 on a 100mhz fsb.
You could try it at 2/3 75 or 83mhz, but that's likely slow the card down. Running it at 1/1 at those speeds is potentially harmful to the card and will most likely void the warranty. Depends on how dangerously you want to live.
Just like CPUs, just because one person got their card to run at a given speed, doesn't mean you will.
A life? Where can I download that?
Where am I going? -- And why am I in this handbasket?