Re: cpufreq for older Toshibas with P3-M and ALi chipset?

[Dag Bakke <dag@bakke.com>]

Dominik Brodowski wrote:

>Hi,
>
>On Sun, Jan 02, 2005 at 05:24:47PM +0100, Dag Bakke wrote:
>  
>
[snip]

>>The laptop appears to work with the 'ACPI Processor P-States driver', 
>>but this only gives me two frequencies to choose between. Is this to be 
>>expected?
>>    
>>
>
>Yes, it is. Mobile Pentium 3 CPU only support two frequency scaling states.
>The 8 states you're seeing using cpuswitch are throttling states -- i.e. the
>CPU is stopped for short periods of time. However, during these periods the
>voltag isn't scaled, so it only leads to a linear reduction of power
>compared to a ~ ^3 reduction if voltage is reduced as well. Furthermore, the
>state the CPU is in when stopped equals the state the CPU is put into when
>there is no work to do -- all this leads to the fact that throttling is
>useless in most cases.
>  
>
I'll test and see how much the drain from the battery changes when using 
cpuswitch. And compare it with the two P-states. Should have done that 
anyway.

>>None of the cpufreq processor drivers appears to fit the bill for a 
>>PIII-M on an ALi chipset, 
>>
[snip]

>Except the acpi-cpufreq driver, there is none you can use with this system.
>
>  
>
>>BTW:
>>I do notice that if I fiddle with the BIOS settings, I can make the 
>>laptop boot at "half speed", coming up at 500 MHz instead of 1000. (As 
>>displayed in /proc/cpuinfo.) And the P-states driver still works, so 
>>presumably it is possible to combine 'native support' and P-states to 
>>obtain 16 steps? :-)
>>    
>>
>
>No :-) Probably this "half speed" mode means the front side bus speed (which
>is multiplied inside the CPU) is put to 50%. And unless you find out how
>this is accessible during a runtime system, there's no chance to combine
>these two.
>
>  
>
Well, I believe it is just the same function as cpuswitch exploits, 
because cpuswitch reports the cpu to be running at 'level 4' when I make 
it boot at 500Mhz.

Thank you for a comprehensive answer, even though it didn't come out as 
positive as I had hoped!

Dag B.