There are some cards out there with dual keying that still only run on 1.5V. Obviously they won't work on a 3.3V only board...

Exactly which dual-keyed cards are showing this behaviour?

So far...
Asus geforce4 4600
Dell OEM geforce2 gts
Asus geforce 4 mx4000

I've got a dell tnt2 in it right now. Had a dell rage 128 pro before that. Both work just fine, but both are the 64bit versions of the cards so I'm trying to find something with putting in the machine. I don't mind picking up another card if they will work, if someone has specific examples to search for through the haze of crippled oem cards.

I guess my next question would be...what would be the fastest or newest card that is 3.3v only that I could use with this board. So far I'm really happy with how rock solid stable the board has been, despite my lack of a decent video card to run it with.

That TNT2-M64 should also be a dual-voltage AGP 4x card. If so the keying/voltage isn't the problem.

What might be: the amount of power those other cards draw. Gf2 GTS and GF4 are pretty heavy by AGP standards, even the Gf4MX might be too much. I can find people mentioning that they have Gf2GTS cards running on P2B boards, but given the number of revisions (almost all related to power supply) that doesn't tell us that much.

Also relevant: what kind of power supply are you using (which brand, model and how much current does it claim to supply on the 5V line)?

Yep, I've also problems with my ASUS P2B and a Geforce 2 GTS. They all disappear when I install a Voodoo3 or a simple S3 agp card...
But I want the GTS there...

I thought I knew for a fact that the ati 9600 only supported 1.5 but then i saw a rare one online that is keyed for both voltages. Whether this is a scam or just additional circuitry to handle the voltage, who knows.