Messages in this thread | | | Date | Tue, 19 Feb 2008 17:52:54 -0600 | From | Robert Hancock <> | Subject | Re: Intel Core2Duo mobile - how does the VID get set? |
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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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