Intel Core2Duo E4400 processors running at different speed?

Question

I was checking my old computer today and I noticed something I tough was kinda strange. The CPU is a Intel Core2Duo E4400 (2M Cache, 2.00 GHz, 800 MHz FSB).

I am running linux so I ran the commands lscpu and cat /proc/cpuinfo, here are the results:

root:~$ lscpu
Architecture:          i686
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                2
On-line CPU(s) list:   0,1
Thread(s) per core:    1
Core(s) per socket:    2
CPU socket(s):         1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 15
Stepping:              2
CPU MHz:               1203.000 <------------||||||||||||
BogoMIPS:              4000.02
L1d cache:             32K
L1i cache:             32K
L2 cache:              2048K

and

root:~$ cat /proc/cpuinfo 
processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 15
model name  : Intel(R) Core(TM)2 CPU          4400  @ 2.00GHz
stepping    : 2
cpu MHz     : 2003.000 <------------||||||||||||
cache size  : 2048 KB
physical id : 0
siblings    : 2
core id     : 0
cpu cores   : 2
apicid      : 0
initial apicid  : 0
fdiv_bug    : no
hlt_bug     : no
f00f_bug    : no
coma_bug    : no
fpu     : yes
fpu_exception   : yes
cpuid level : 10
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm lahf_lm dts
bogomips    : 3999.96
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          4400  @ 2.00GHz
stepping    : 2
cpu MHz     : 1203.000 <------------||||||||||||
cache size  : 2048 KB
physical id : 0
siblings    : 2
core id     : 1
cpu cores   : 2
apicid      : 1
initial apicid  : 1
fdiv_bug    : no
hlt_bug     : no
f00f_bug    : no
coma_bug    : no
fpu     : yes
fpu_exception   : yes
cpuid level : 10
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm lahf_lm dts
bogomips    : 4000.02
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

Notice how the first processor in the command cat /proc/cpuinfo says 2003MHz and the second one 1203MHz.

Is this normal?

Also, the first one not always show 2003MHz, sometimes both show 1203MHz. I am using Ubuntu 11.10.

xsensors command show that the processors run at 45C to 55C degrees (we are in summer here).

Answer 1

Yes, this is normal. Linux can change clock frequency, or voltage, to preserve energy. Too see current frequency, you can take a look at cpufreq-info

Answer 2

Yes, this is normal.

Modern processors can "underclock" themselves in order to save power and keep the processor cool. The processor can change clock speed many times a second depending on cpu load and so you may find that repeatedly checking the speed on one or both of the method you used will give different readings at different times.

It is also possible that the 2GHz reading is the maximum speed reported by the processor itself rather than the current "dynamic" clock speed.