Originally Posted by sinnedone
Is there anything online that explains what the c states do and how they interact with windows?
Windows interacts with C-states, not the other way around. You might find in your BIOS that when disabling C3/C6 it says something like "Disable C3 Reporting". IOW C-states are not disabled, instead when the BIOS hands off to the OS it just doesn't inform it of the idle state(s). If Windows doesn't know about them then it doesn't use them.
Very basically, CPU core C1 stops the core clock, better known as "Halt", when all cores are at C1 state or higher and C1E is enabled then as well as stopping the clocks the voltage can be lowered to that of the LFM (VID that is associated with the lowest frequency mode, typically 1.6GHz for SNB/IVB). IIRC C3 also flushes L1/L2 and C6 additionally turns off supplies internally.
So when you think your CPU is idling at 1.6GHz it is most probably not running at all (0GHz). When you use software like cpu-z to measure frequency it needs to wake up the core(s) to read the registers. (catch 22). IIRC software such as Throttlestop and maybe Realtemp will show the time that the CPU spends in each C-State.
For using stepped turbo's you need the higher C-states enabled. For instance my 2500k gets quite hot for me at 4.6GHz with all 4 cores heavily loaded so I don't want to run 4 cores higher than that but if I'm only using one core it runs at 5.0GHz. For my P67/2500k no EIST, regular LLC (Intel spec) no C1E, C3/C6 reporting, -0.005V offset and 0.25V additional turbo voltage.
For LLC you might find this interesting http://www.anandtech.com/show/2404/5
and http://www.anandtech.com/show/2404/6Edited by ucode - 2/5/13 at 10:32pm