[coreboot] ACPI on m57sli v1.0

[Rudolf Marek]

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Hi I was X-AFK.

>> One thing I would like to ask, not just regarding this motherboard but
>> all AM2/AM2+/AM3 boards.
>> Would it be possible to implement a feature that would allow us to
>> configure custom P-States to save on CMOS, other than what the
>> manufacturer specifies? Most BIOS allow setting lower and higher
>> multipliers than stock on some CPUs but disable CPU power management
>> altogether when doing so. It would be quite a leap forward, when
>> compared with vendor BIOS to be able to specify at least one VID and
>> FID for the high power state and another FID and VID for the low power
>> state.

Yes it would be possible.

>> With overclocking the benefits are enormous in the power bill and also
>> for the low power state, since the manufacturer specifies 1.1v @ 1GHz
>> and most CPUs handle 0.8v @ 800MHz quite easily. I'd love to get those
>> low power states on my home server :)

Aha have you the revisionG? What about idle=halt. We can fine tune what the CPU
will do when doing C1 (HLT) we change the PMM register values to more aggressive
power save. Enabling the ALTvid maybe?

> I've been trying to get hold of one of these M57SLI-S4 boards to try
>> and implement this but would like to know if this is something
>> possible to achieve with the current code base.

Yes it is. The acpigen generator will generate any ACPI powerstates you
want/need. The ACPIgen generator is simply capable of generating the data
structures which are holding the power state values. By altering the algorithm
for P states, you can then create your own custom values. Problem is if the CPU
will allow the "underclocking" sometimes it wont transition to any fid which is
lower then minFID or startFID. Please consult the CPU manual (BKDG).
For the Pstates algo - 10.5.1.1 P-state Recognition Algorithm and the "portal"
frequencies to see how the VCO and core frequency differs.

If you have revisionG CPU (dualcore) maybe it would be quite cool to implement
the C1E state. This could save much more power.

Rudolf
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