Re: Intel Core2Duo mobile - how does the VID get set?

[Robert Hancock]

Brian Morrison wrote:
> Pallipadi, Venkatesh wrote:
>
> > > After a fair bit of Googling and reading around, I'm none the wiser 
> > > about exactly how Linux 2.6.x sets the processor VID (or for that 
> > > matter how it decides the FID settings) when using the ondemand 
> > > governor and cpufreq stuff.
> > >
> > > Can anyone tell me a) whether this is obtained from the BIOS, 
> > > something in the MSR of the processor or elsewhere and
> >
> > Yes. The freq and voltage supported comes from the platform BIOS. BIOS
> > exports this in an ACPI table which is handled by acpi-cpufreq driver in
> > Linux kernel.
>
> OK, thanks for that.
>
> >  
> > > b) whether there is an interface in /proc or /sys where one can find 
> > > out what is set and modify it?
> >
> > There is no way of modifying and using new VIDs etc in Linux kernel
> > (other than exporting your own DSDT and hacking the related code).
>
> Is there a way of viewing the ACPI table contents relating to the VIDs
> and FIDs?

Viewing the decompiled ACPI DSDT may provide some hints, however the 
kernel itself knows nothing about VID/FID settings for acpi-cpufreq, 
basically the kernel writes to magic ACPI registers and the BIOS or 
hardware take over to do what's required..
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