Is the C3 possible with SMP?

Alexander Motin mav at
Sun Nov 2 10:46:34 PST 2008


I have tried to enable C3 state on my Core2Duo laptop and found that it 
is not working good. System HZ timer stops during CPU sleep. After some 
investigation I have found that it is due to LAPIC timer used for HZ 
stopped during C3 state (same as during AMD's C1E).

So the question is: Is it possible (or planned) to make it work somehow? 
For example, by using some external timer instead of LAPIC's one?

ACPI reports about 20% less idle power consumption with C3 state 
comparing to C2. It would be interesting to get additional half an hour 
on battery.

Alexander Motin

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