And, this problem hits us because Linux 2.4 kernels compiled with a Pentium-Classic or higher Processor family kernel configuration setting will automatically take advantage of extended paging (for kernel hackers out there, this is the X86_FEATURE_PSE constant defined in include/asm-i386/cpufeature.h.) Fortunately, there is a quick and easy fix for this problem. If you have been experiencing lockups on your Athlon, Duron or Athlon MP system when using AGP video, try passing the mem=nopentium option to your kernel (using GRUB or LILO) at boot-time. This tells Linux to go back to using 4K pages, avoiding this CPU bug. In addition, it should also be possible to avoid this problem by not using AGP on affected systems.
Needless to say, this is a problem that affects many Linux gamers. The update also states that Alan Cox will be adding detection code in the kernel to avoid this issue altogether.