Crash knows way more about this stuff than I do, I simply speak from my personal experience. I don't know about your
M/B or FSB multipliers. But I do remember that the first GeForce I installed (year n half ago) had a little 250watt
power supply for both the Athlon800 and Geforce....and it did just exactly what you described. The higher I tried to clock the card...the lower the frame rates became. A better
power supply fixed the problem entirely.
...Just thought I'd throw that in there because I see very little difference between 2x and 4x AGP. But I saw a hellof
a difference when my card was underpowered. That's another reason I like asus drivers...they report my Vcard voltage.
I thought I was wrong once, but I was mistaken.