Need definitive info on Haswell C6 and C7 c-states

[flexy]

I have a Asus Z87-Pro board that supports those c-states. However, I read a lot about those c-states and there is still something unclear to me:

* Are C6 and C7 even relevant for desktop systems?

* Do C6 and C7 come only into play when the system hibernates/sleeps but NOT in normal CPU idling mode like on the desktop?

I can enable C6 and C7 "Package" c-states in the BIOS and the PSU is also said to support them.

However I do *never* see those PACKAGE c-states active (throttle stop etc.), "only" (?) C7 for core C-states. But then I dont use hibernate and sleep

According to throttle stop I can "only" (?) go down to C2 package cstates and this doesn't seem very low to me.

 

[ShintaiDK]

You cant get C7 state with a discrete GPU to begin with.

1. Not really.
2. Correct.

You cant see anything below C2 because the system is in sleep mode.

 

[flexy]

thanks, helped me a lot!

 

[Chesebert]

My 4790k shows 0v on one or more core in idle/single threaded app. I think that's C6. I think C7 flushes the L3 cache which happens during sleep.