CPU C4 vs. C3 states, BIOS support and 1.5W power savings

[Thomas Meyer]

Török Edvin schrieb:
> On 6/21/07, ja at disorder.sk <ja at disorder.sk> wrote:
>>
>> Not at all, still the same.
>
> Then maybe your BIOS correctly reports C4 through acpi. BTW I tested
> on a Dell Inspiron 6400.
> ACPI reports 3 c-states in dmesg:
>
> ACPI: CPU0 (power states: C1[C1] C2[C2] C3[C3])
> ACPI: Processor [CPU0] (supports 8 throttling states)
> ACPI: CPU1 (power states: C1[C1] C2[C2] C3[C3])
> ACPI: Processor [CPU1] (supports 8 throttling states)
>
> Also /proc/acpi/processor/CPU0/power:
> active state:            C0
> max_cstate:              C8
> bus master activity:     00000000
> maximum allowed latency: 8000 usec
> states:
>    C1:                  type[C1] promotion[--] demotion[--]
> latency[001] usage[00004077] duration[00000000000000000000]
>    C2:                  type[C2] promotion[--] demotion[--]
> latency[001] usage[04337133] duration[00000000007870996131]
>    C3:                  type[C3] promotion[--] demotion[--]
> latency[085] usage[02418145] duration[00000000013129058814]
>
> Could you please check your dmesg output, and see how many C-states it
> reports?

To make it clear to anybody:

The reported ACPI state has absolutely nothing to do with the connected
CPU MWAIT state. It's defined in the ACPI firmware which value is passed
to the MWAIT command for which ACPI C-state!

So for the macbook pro C3 will put the Intel Core cpu into CPU C-state C4.

Please stop confusing ACPI c-states with CPU c-states.

mfg
thomas