Performance of MSI K8NGM2-FID motherboard with amd64, 686, and k7 kernels
I can crank up the CPU-LDT frequency to 215 in BIOS and that seems to work as reliably as the default, non-overclocked setting of 200. This translates to a CPU speed of 2150 MHz. I have done memory and CPU burn in tests at this MHz and all tests have passed. If I push it up to 220 (which would be a CPU speed of 2200 MHz), the system sometimes fails to boot.
With the SMP version of all kernels, both cores are detected properly and used.
I tested the amd64 (k8), 686, and k7 kernels with the nbench tool, a derivative of the old Byte benchmark. Here is what I found:
OS : Linux 2.6.15-25-686 C compiler : gcc version 4.0.3 (Ubuntu 4.0.3-1ubuntu5) libc : libc-2.3.6.so MEMORY INDEX : 14.711 INTEGER INDEX : 13.313 FLOATING-POINT INDEX: 23.301
OS : Linux 2.6.15-25-k7 C compiler : gcc version 4.0.3 (Ubuntu 4.0.3-1ubuntu5) libc : libc-2.3.6.so MEMORY INDEX : 14.755 INTEGER INDEX : 13.218 FLOATING-POINT INDEX: 23.323
OS : Linux 2.6.15-25-amd64-k8 C compiler : gcc version 4.0.3 (Ubuntu 4.0.3-1ubuntu5) libc : libc-2.3.6.so MEMORY INDEX : 17.346 INTEGER INDEX : 15.108 FLOATING-POINT INDEX: 23.600
As you can see, the best performance is seen running the processor in native amd64 mode, but the difference isn't huge (about 1% for floating point, 12% for integer, and 15% for memory access). Remember that this is on an essentially 32 bit application that is merely recompiled for each architecture. There are no specifically 64-bit optimizations in the code.
CPU frequency autoscaling
In amd64 mode (-k8 Linux kernel) I was surprised to find when I cat'ed /proc/cpuinfo that the processor was running at 1075 MHz--half speed! When system load went up, inspection of /proc/cpuinfo shows the MHz figures stepping up to the maximum, 2150 MHz. Very nice! In -k7 mode, the powernowd daemon claims that the processor is capable of power management, however I never saw the CPU MHz actually change in /proc/cpuinfo. Eventually I figured out that with the k7 kernel and the 686 kernel the CPU MHz figure stays the same as the CPU scales, but the bogomips figure changes. So, it appears that CPU frequency scaling is happening with all kernels, but pay attention to the bogomips line in /proc/cpuinfo, rather than the MHz line, to make sure.
Of course, make sure that Cool'n'Quiet is enabled in the BIOS, otherwise no CPU frequency scaling seems to occur.
Related:Installing Ubuntu on MSI K8NGM2-FID motherboard with AMD Athlon 64 X2 3800+