support for Intel(R) Celeron(R) M in kernel 2.6.11
Hi, all!
I just both a new laptop and of course installed Linux on it. It has a
Intel Celeron M processor, and I can't quite figure out what it is
capable of. I'm running kernel 2.6.11. The only power saving feature
I have managed to get working is frequency scaling using the
p4-clockmod module. When I install it I get the warning:
p4-clockmod: Warning: Pentium M detected. The speedstep_centrino
module offers voltage scaling in addition of frequency scaling. You
should use that instead of p4-clockmod, if possible.
p4-clockmod: P4/Xeon(TM) CPU On-Demand Clock Modulation available
If I try to load the speedstep_centrino module, I get the error:
FATAL: Error inserting speedstep_centrino: No such device
What I've managed to find out, is that the Celeron M processors don't
have the 'SpeedStep' technology, it's only included in the Pentium Ms.
But excluding some marketing talk, I couldn't figure out what EXACTLY
'Speedstep' ot 'Enchanced Speedstep' is. The most useful doc I got my
hands on is a feature comparision table of the Celeron M and Pentium
M processors at
http://support.intel.com/support/processors/mobile/pm/sb/CS-007967.htm
According to this my CPU does not have 'SpeedStep' but has Mobile
Voltage Positioning - MVP IV. It has family/model/stepping of
6/13/16 and is identified (incorrectly, I think) as a DOTHAN_B0 by
speedstep_centrino.c.
Here's the output of 'cat /proc/cpuinfo':
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 13
model name : Intel(R) Celeron(R) M processor 1.30GHz
stepping : 6
cpu MHz : 162.168
cache size : 1024 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr mce cx8 apic mtrr pge mca
cmov pat clflush dts acpi mmx fxsr sse sse2 ss tm pbe
bogomips : 2555.90
Is MVP the official name for what in the linux kernel is refered to as
voltage scaling? Does this CPU have 'voltage scaling' and if yes, how
can I get it to work under Linux. If the Celeron Ms have frequency
scaling (which they obviously do) and MVP (supposedly voltage
scaling), then what is this '(Enchanced) SpeedStep' thing which they
don't have?
Any ideas/solutions are welcome!
Best regards,
Rado
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