One thing I mentioned to rge is that how Windows is set up also plays a part in your actual multiplier at idle. If you have C1E and Speedstep enabled in the bios, you will also need to have your Power Options set appropriately so your multi isn't jumping up and down at idle.
In XP set your Power Options like this to get the full effect of C1E and the lower power states:
The picture is of my Q6600 dropping from 9.0 to 6.0.
http://img380.imageshack.us/img380/5580/q6600c1ern4.png
For Vista you need to reduce your Minimum Processor State:
http://img258.imageshack.us/img258/7249/vistac1ehf1.png
If RealTemp is reporting that your multi is jumping up and down it's because it is jumping up and down. I decided to let RealTemp start telling it like it is and then users will at least know exactly what's going on and they can decide what needs to be adjusted in the bios or Windows or both.
Edit: Another thing that rge has noticed is some of the numbers displayed by CPU-Z simply don't add up. It seems to be using multipliers of 1/2, 1/4, 1/8 or even 1/16 internally in some of its calculations:
http://img367.imageshack.us/img367/896/rgegc1.jpg
196.0 X 21 does not equal 4111.5.
It equals 4116.0 MHz