Re: Any Riva TNT2 M64 upgrades?
Well I've got a box sitting in the corner with a 6600GT running on an old KT133A board with a 900mhz Duron, all powered by a 200w junk PSU and it plays old games just fine. I even hooked up the auxiliary 12v line. Completely stupid, but it works.
I doubt an Athlon XP in my system would pair up well with such the little PSU (it draws much more wattage), so there's probably a practical limit of how much room your CPU leaves for a video card. The older Athlons and P4's drew much more power.
If you want to be absolutely safe, anything without an auxillary 4-pin connector should work just fine. I've got an FX 5700 that was fanless and needed no extra connector. I've also seen the same in 7600GS AGP's.