No c2-c7 states on core i7

[Erik Slagter <erik@slagter.name>]

Hi there,

I already put on my flame retardant underwear, I know this is a FAQ, but 
I really need a bit of a jumpstart, google won't tell me where to start, 
so please be gentle ;-)

I bought a Gigabyte EX58-UD3R motherboard recently and put a core i7 920 
on it. This seems to be a fairly common combination.

In short: I know the core i7 does implement several C-states, from 
memory c1, c1e, c3, c6 and c7. Linux (vanilla, 2.6.31.6) does not 
recognise any of them.

The kernel configuration is very similar to the one I am running on my 
laptop with a recent mobile core2duo processor, and this one reports 
C1,C2,C3 (although it should also report yet another C state, but I 
guess that one is disabled by the bios or something alike).

Is this normal (WIP?)?

If not, where should I start debugging? I know there is "something" with 
decoding the DSDT table, but what should I look for?

I seem to remember that with an earlier linux version (before 2.6.30.5) 
it actually did work, but I am not completely sure.

Thanks for your help in advance!

Additional info that might be useful:

- all options related to power saving and C-states are ENABLED in the BIOS
- all options related to power management and idling are ENABLED in the 
kernel, which runs in 64 bits mode
- frequency switching runs fine using acpi-cpufreq and ondemand governor

If I compare the dmesg from both computers after booting, the laptop 
says "ACPI: CPU1 (power states: C1[C1] C2[C2] C3[C3])" at some point, 
this message is not output at all by the server.

Output from proc/acpi/processor/CPU0/info
processor id:            0
acpi id:                 0
bus mastering control:   yes
power management:        no
throttling control:      yes
limit interface:         yes

Output from proc/acpi/processor/CPU0/power
active state:            C0
max_cstate:              C8
maximum allowed latency: 2000000000 usec
states:
     C1:                  type[C1] promotion[--] demotion[--] 
latency[000] usage[00000000] duration[00000000000000000000]