Read the docs and follow the procedure as outlined there.
I have found that with an open case when you bring a Q6600 down to 1600 MHz and about 1.10 volts you should see idle temps about 5C or 6C above your air temp with a good air cooler. If you have a good water cooling system then try to get RealTemp to report idle temp on all 4 cores at about 4C above your water temp. It's not an exact science but a guide line which will get you pretty close to the real temperature.
Individually adjust your Idle Calibration factors to get all 4 cores equalized at Idle. This calibration will improve the accuracy of your reported temperatures from idle to TjMax.
Edit: I did a quick calibration of my Q6600 about 30 pages ago. I got lucky and found it on my second try!
http://www.xtremesystems.org/forums/...postcount=1006
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