PROBLEM: /proc/cpuinfo reports erroneous CPU frequency. (2.6.23 & 2.6.22)

PROBLEM: /proc/cpuinfo reports erroneous CPU frequency. (2.6.23 & 2.6.22)

[Alexander Rajula]

While using 2.6.23 and 2.6.22 (earlier kernels have not been tested) /proc/cpuinfo reports the wrong CPU frequency:


While overclocking an AMD Athlon X2 (2GHz) CPU /proc/cpuinfo reports the wrong CPU frequency.
I am quite puzzled by this.
Is this an error in the kernel, or is there something strange going on?


Output from /proc/cpuinfo (processor at 3.0GHz in BIOS):

processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 75
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
stepping        : 2
cpu MHz         : 2300.043
cache size      : 512 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow rep_good pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy
bogomips        : 4602.12
TLB size        : 1024 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm stc

processor       : 1
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 75
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
stepping        : 2
cpu MHz         : 2300.043
cache size      : 512 KB
physical id     : 0
siblings        : 2
core id         : 1
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow rep_good pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy
bogomips        : 4599.31
TLB size        : 1024 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp tm st



Output from scripts/ver_linux:

Linux dubbelmacka 2.6.23-gentoo-r3 #3 SMP PREEMPT Mon Dec 10 00:46:09 CET 2007 x
86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ AuthenticAMD GNU/Linux
 
Gnu C                  4.1.2
Gnu make               3.81
binutils               Binutils
util-linux             2.12r
mount                  2.12r
module-init-tools      3.2.2
e2fsprogs              1.39
reiserfsprogs          3.6.19
reiser4progs           1.0.5
PPP                    2.4.4
Linux C Library        2.5
Dynamic linker (ldd)   2.5
Procps                 3.2.7
Net-tools              1.60
Kbd                    1.13
Sh-utils               6.9
udev                   115
Modules Loaded         nvidia

Re: PROBLEM: /proc/cpuinfo reports erroneous CPU frequency. (2.6.23 & 2.6.22)

[Frans Pop]

Alexander Rajula wrote:
> While overclocking an AMD Athlon X2 (2GHz) CPU /proc/cpuinfo reports the
> wrong CPU frequency. I am quite puzzled by this.
> Is this an error in the kernel, or is there something strange going on?

You may want to read some old threads on this list and check if that matches
what you are seeing:
http://lkml.org/lkml/2006/3/29/150
http://lkml.org/lkml/2006/10/26/182

Cheers,
FJP

Re: PROBLEM: /proc/cpuinfo reports erroneous CPU frequency. (2.6.23 & 2.6.22)

[Dave Jones]

On Mon, Dec 10, 2007 at 02:48:54AM +0100, Alexander Rajula wrote:
 > While using 2.6.23 and 2.6.22 (earlier kernels have not been tested) /proc/cpuinfo reports the wrong CPU frequency:
 > 
 > 
 > While overclocking an AMD Athlon X2 (2GHz) CPU /proc/cpuinfo reports the wrong CPU frequency.
 > I am quite puzzled by this.
 > Is this an error in the kernel, or is there something strange going on?

cpu frequency scaling relies on static tables in the BIOS that contain
a bunch of predefined frequencies. When you overclock, you're running
at frequencies that aren't in these tables.  Everything falls apart as a result.

There's nothing here to fix, don't overclock.

	Dave

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