3.2GHz cpus with cpufreq become 2.8GHz

[Krzysztof Oledzki <olel@ans.pl>]

Hello,

I have just noticed that enabling cpufreq on my Dell PowerEdge 1425SC 
changes my secondary cpu clock to 2.8GHz.

# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.20GHz
stepping        : 3
cpu MHz         : 3200.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
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 pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr
bogomips        : 6403.72

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.20GHz
stepping        : 3
cpu MHz         : 3200.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
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 pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr
bogomips        : 6400.24

processor       : 2
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.20GHz
stepping        : 3
cpu MHz         : 2800.000
cache size      : 2048 KB
physical id     : 3
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
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 pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr
bogomips        : 6400.30

processor       : 3
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.20GHz
stepping        : 3
cpu MHz         : 2800.000
cache size      : 2048 KB
physical id     : 3
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
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 pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr
bogomips        : 6400.29

According to cpuinfo the primary CPU (two HT logical CPUs) works with 
3.2GHz clock but the secondary works with 2.8GHz.

What is also strange, this 3.2GHz freq is not listed on 
scaling_available_frequencies for both CPUs:

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
p4-clockmod

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
350000 700000 1050000 1400000 1750000 2100000 2450000 2800000

# cat /sys/devices/system/cpu/cpu2/cpufreq/scaling_driver
p4-clockmod
# cat /sys/devices/system/cpu/cpu2/cpufreq/scaling_available_frequencies
350000 700000 1050000 1400000 1750000 2100000 2450000 2800000

I can confirm that this problem exists on 2.6.16/2.6.17/2.6.18 (just 
tested). Is it a problem with BIOS or p4-clockmod cpufreq driver?

Best regards,


				Krzysztof Olędzki