I have now tested yet another machine (we were a couple of guys in need for more oomph
), and it appears that it is indeed the CPU which is responsible for our woes. Here it goes:
My machine and one of the others are Stepping 10, while one is Stepping 8. Both Stepping 10 processors (all AMD64 3200+) failed with the exact same behaviour as described earlier, while the Stepping 8 CPU did just fine.
Memtest shows slightly different memory access values between the two different steppings: Stepping 10 is slightly slower accessing RAM and a bit faster accessing L2 cache.
Maybe the memory timing has something to do with the nvidia driver. Has anyone else here the opportunity to test different chips? I will write to NVIDIA tomorrow to tell them about this. Maybe others can do too.