On 06/22/2009 12:54 AM, Mahmood Naderan wrote:
Hi, My first question was why CPU states are different from BIOS? If C4 and C5 are good, why and for what reason, the BIOS does not support it. This means that BIOS does not like power saving sates (!) After that I wondered why my system does not even support C3. So you and Edward said that C3 is mapped to C6. It is understanable that OS map C3 to C6, but since ACPI is a standard, why should CPU, BIOS and OS each one say something different. I am not so expert but I think it is a little bit confusing.
It's the BIOS that does the mapping in terms of what C-states are exposed to the OS. Before ACPI 2.0, only C-states up to C3 were defined. ACPI 2.0 allows more C-states, but I don't know if Windows actually supports them. (Not sure if Windows has full ACPI 2.0 support yet.) That may be why the BIOS people did it that way.
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