hardware limits

hardware limits

[Niels Borne]

Hi there,

I am working on a vaio laptop pcg-fr415b, using fc5 (see result of cat 
/proc/cpuinfo above).
Since it is quite noisy I allowed cpuspeed at startup and this improved 
the situation a little bit.
Still cpufreq-info (see details above -in french, but you can guess) gives
hardware limits : 2.10 GHz - 2.80 GHz
Is there any hope to go below 2.10 GHz and if yes, how ?

Thanks,

Niels









cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Celeron(R) CPU 2.80GHz
stepping        : 9
cpu MHz         : 2100.000
cache size      : 128 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 pae mce cx8 mtrr pge mca cmov 
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
bogomips        : 5589.50



cpufreq-info
cpufrequtils 0.4: cpufreq-info (C) Dominik Brodowski 2004
Veuillez rapportez les erreurs et les bogues à linux@brodo.de, s'il vous 
plait.
analyse du CPU 0 :
   pilote : p4-clockmod
   CPUs qui doivent changer de fréquences en même temps : 0
   limitation matérielle : 2.10 GHz - 2.80 GHz
   plage de fréquence : 2.10 GHz, 2.45 GHz, 2.80 GHz
   régulateurs disponibles : userspace, performance
   tactique actuelle : la fréquence doit être comprise entre 2.10 GHz et 
2.80 GHz.
                   Le régulateur "userspace" est libre de choisir la vitesse
                   dans cette plage de fréquences.
   la fréquence actuelle de ce CPU est 2.10 GHz.

Re: hardware limits

[Dominik Brodowski]

Hi,

On Sun, May 28, 2006 at 09:37:11AM +0200, Niels Borne wrote:
> I am working on a vaio laptop pcg-fr415b, using fc5 (see result of cat 
> /proc/cpuinfo above).
> Since it is quite noisy I allowed cpuspeed at startup and this improved 
> the situation a little bit.
> Still cpufreq-info (see details above -in french, but you can guess) gives
> hardware limits : 2.10 GHz - 2.80 GHz
> Is there any hope to go below 2.10 GHz and if yes, how ?

Unfortunately no -- there's a bug in the hardware which causes problems if
the frequency is lower than 2 GHz. Also, p4-clockmod doesn't save you all
that much (if at all) as it doesn't do CPU frequency and voltage scaling, so
you shouldn't worry too much about this...

	Dominik

Re: hardware limits

[Niels Borne]

Hi,

Thanks for your answer. More questions below :


Dominik Brodowski a écrit :
> Hi,
> 
> On Sun, May 28, 2006 at 09:37:11AM +0200, Niels Borne wrote:
>> I am working on a vaio laptop pcg-fr415b, using fc5 (see result of cat 
>> /proc/cpuinfo above).
>> Since it is quite noisy I allowed cpuspeed at startup and this improved 
>> the situation a little bit.
>> Still cpufreq-info (see details above -in french, but you can guess) gives
>> hardware limits : 2.10 GHz - 2.80 GHz
>> Is there any hope to go below 2.10 GHz and if yes, how ?
> 
> Unfortunately no -- there's a bug in the hardware which causes problems if
> the frequency is lower than 2 GHz. 

Which hardware exactly ? It this related to the N60 errata ?

Also, p4-clockmod doesn't save you all
> that much (if at all) 

well it seems to improve somewhat

as it doesn't do CPU frequency and voltage scaling,

what do you mean ? my frequency is now most often 2.10 GHz, and was 2.80 
GHz, so it does CPU frequency, doesn't it ?


so you shouldn't worry too much about this...


> 
> 	Dominik

Niels

Re: hardware limits

[Dominik Brodowski]

Hi,

On Sat, Jun 03, 2006 at 04:47:16PM +0200, Niels Borne wrote:
> >On Sun, May 28, 2006 at 09:37:11AM +0200, Niels Borne wrote:
> >>I am working on a vaio laptop pcg-fr415b, using fc5 (see result of cat 
> >>/proc/cpuinfo above).
> >>Since it is quite noisy I allowed cpuspeed at startup and this improved 
> >>the situation a little bit.
> >>Still cpufreq-info (see details above -in french, but you can guess) gives
> >>hardware limits : 2.10 GHz - 2.80 GHz
> >>Is there any hope to go below 2.10 GHz and if yes, how ?
> >
> >Unfortunately no -- there's a bug in the hardware which causes problems if
> >the frequency is lower than 2 GHz. 
> 
> Which hardware exactly ? It this related to the N60 errata ?

Yes, that's the N60 errata.

> Also, p4-clockmod doesn't save you all
> >that much (if at all) 
> 
> well it seems to improve somewhat
> 
> as it doesn't do CPU frequency and voltage scaling,
> 
> what do you mean ? my frequency is now most often 2.10 GHz, and was 2.80 
> GHz, so it does CPU frequency, doesn't it ?

It doesn't scale the frequency, it throttles it -- and that means that the
voltage cannot be dropped:

"In contrast to CPU frequency scaling, where the operating frequency is
constantly modulated, throttling means the CPU is forced to a halt for short
periods of time. If throttled, the CPU [enters] into a physical and
electrical state comparable to the idling states mentioned above, so it can
be described as an enforced idling of the CPU.

As certain CPU power state typically utilize similar hardware
implementations, and as throttling does not have a positive effect on the
energy consumption during CPU power states, throttling the CPU by a given
rate is only useful if the CPU is less idle than the throttling rate."


	Dominik