/proc/cpu info reports erroneous cpu speed

[parish]

I put together a new system so my sons and I could do a bit of overclocking experimentation and in the process discovered that the system speed reported in /proc/cpuinfo seems to always assume a multiplier of x9, regardless of what is actually set in the BIOS. The board defaults to 333 MHz x9, for a system speed of 3 GHz, which is correctly reported in cpuinfo. When I bump the FSB to 500 MHz and drop the multiplier to x6, however, instead of the expected 500 MHz x6 = 3 GHz, cpuinfo reports the system speed as 4.5 GHz!

As much as I like the idea that I can overclock a 3 Ghz C2D processor to 4.5 GHz without having to bump up Vcpu significantly, it doesn't seem very likely. This is supported by memtest86+ v2.00 output and a few super_pi benchmarks I performed that are consistent with the expected 500 x6 = 3 GHz system speed.

Any ideas of what might be causing this or, even better, what I might do to correct it?

Thanks.

Daniel

[sideways]

When you overclock and want correct cpuinfo stats I think you need to disable cpu frequency scaling in the bios, it's called 'Cool 'n Quiet' on AMD boards, will be something else for an intel based board.

If peformance is improved I wouldn't worry about it too much. (Is bogomips improved? Have you run some benchmarks?)

[parish]

I think this may be called Frequency Unlimit in my Bios (the board is a Foxconn Mars, bios G29 beta) and it is disabled. In fact I had to disable all cpu-related settings other than core multiprocessing in order to get the system speeds reported accurately in XP, I was just hoping that it had fixed this problem in linux as well, but it did not.

System performance has not improved as yet, because I'm stilling running at 3 GHz, just with a faster FSB and lower multiplier (500 x6 vs 333 x9). In fedora, lshw reports the correct bus speed (500 MHz), but cpuinfo gives my system speed as 4.5 GHz, which is incorrect. Memtest and super_pi benchmarks (performed in fedora) show that the system speed is 3 GHz.

It's not really a big deal. I'm just playing around with a bit of overclocking and would prefer to do it all in fedora, but the (overclocking) tools and community support are far more developed in the windows world. I'll just set my machine up to dual boot until I've got the settings I like and then windows will be back to gathering dust.

Daniel

[sej7278]

have you made sure the cpuspeed service is not running?

when i overclocked my 3ghz p4 prescott, the cpuinfo correctly stated 3.4ghz.

[parish]

have you made sure the cpuspeed service is not running?

when i overclocked my 3ghz p4 prescott, the cpuinfo correctly stated 3.4ghz.

Good suggestion, but unfortunately it is already turned off so that's not the solution for me.

Daniel