Even with mem=nopentium, my system reboots instantly upon entering into a game (i.e., just before the first 3d display should appear) in the latest Tribes 2 beta patch for Linux.
Here's my stats, again:
Latest NVidia drivers
Option NvAgp = 0 or 2, both crash
mem=nopentium, still crash, at least in Tribes2
This is on a 1ghz Athlon, not XP or MP, on a Epox
8Kta3+ running a KT133A chipset.
Here's hoping that NVidia knows that they have a real problem on Athlon.