Missing megahertz in /proc/cpuinfo on AMD64 chips
 

Someone please help put my adled brain to rest regarding this issue.

Using slackware 11.0, a default 2.4.33.3 kernel install tells me that /proc/cpuinfo shows my Athlon 64 3200+ as 2010.335 MHz.

That same install on an Opteron 148 at 2.2GHZ shows /proc/cpuinfo at 1001.000 MHz.

What did I do wrong?

I know there is some ACPI funkogistics going on here, as an Ubuntu 6.10 install lists /proc/cpuinfo at 1GHz on each chip. But if I run an intensive enough session and make the CPU burst up to 100%, the same /proc/cpuinfo shows the 3200+/148 chips as 2GHz/2.2GHz respectively during the burst. They both throttle back down to 1GHz after the session is over.

This does not occur on a default Slackware 11.0 install utilizing the 2.4.33.3 kernel on the Opteron 148. The 3200+ is listed out of the box @ 2GHz. The 148 is listed @ 1GHz. When I burst the CPU, the 3200+ reports correctly @ 2GHz; the 148 reports @ 1GHz.

What am I missing here?

ACPI, and in particular, "Cool 'n' Quiet", AMD's equivalent to Intel's SpeedStep.

Basically, when the processor is not doing anything, under a 2.6 kernel with Cool'n'Quiet enabled, Linux (via ACPI) switches the processor to a lower frequency mode when it's not doing very much. When work is required, the processor switches back to the faster mode, and when finished, back down again, and so forth.

The 2.4 kernels ACPI support is not as well developed as that of the 2.6 series - so with the 2.4 kernels, the processor is left running at full speed instead.

Your Athlon64 3200+ is already running at full speed, there is nothing wrong with your kernel there. For the Opteron, it's already answered.

Thanks for the replies. The Opteron is showing up correctly now. Not sure what happened, I just powered the box down and let it sit overnight. When I booted it the next morning /proc/cpuinfo listed it correctlyl at 2211.368.