cpufreq scaling appears not to work on overclocked systems

cpufreq scaling appears not to work on overclocked systems

[Berck E. Nash]

This is not new, but exists as far back as 2.6.17.  I haven't reported
it before because I figured that surely someone else had noticed it, but
since it's still unfixed and I cannot find any mention of it on LKML,
here we go.

I'm running a Core2 Duo 1.86GHz overclocked to 2.56GHz.  Everything is
normal with cpufreq scaling disabled.  With cpufreq scaling enabled in
the kernel, using any governor, /proc/cpuinfo indicates a maximum of the
rated frequency rather than the actual frequency.

Here it is under 100% utilization, with userspace governor and powernowd:

berck@luna:~$ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Core(TM)2 CPU          6300  @ 1.86GHz
stepping        : 6
cpu MHz         : 1862.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall
lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
bogomips        : 5134.39
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Core(TM)2 CPU          6300  @ 1.86GHz
stepping        : 6
cpu MHz         : 1862.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 1
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall
lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
bogomips        : 5131.64
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

At idle it drops down to 1596.000 MHz reported.  At boot the kernel
doest report the correct frequency (2564.907), which agrees with the
bogomips reported by /proc/cpuinfo as well.

I haven't done any benchmarking to try to determine if perhaps freq
scaling works as it should and just the reported frequency is incorrect.

Berck

Re: cpufreq scaling appears not to work on overclocked systems

[Dave Jones]

On Sun, Jul 29, 2007 at 03:16:45PM -0600, Berck E. Nash wrote:

 > I'm running a Core2 Duo 1.86GHz overclocked to 2.56GHz.  Everything is
 > normal with cpufreq scaling disabled.  With cpufreq scaling enabled in
 > the kernel, using any governor, /proc/cpuinfo indicates a maximum of the
 > rated frequency rather than the actual frequency.

FAQ.
The BIOS contains hard coded tables of frequencies.
Just because you changed the clocks on which those tables
are based doesn't mean the tables will change.

Not a bug.

	Dave

-- 
http://www.codemonkey.org.uk