Here's an interesting test. I'm running one thread of Prime95 and I have it locked to core 0 on my Q6600. Because a Quad core consists of two Dual Cores inside, you can see that core 0 and core 1 are locked together. The funny thing is that core 2 and core 3 are not at the full multiplier. If my motherboard would let them, they would rather be closer to 6.0 in an idle state. Their buddies, core 0 and core 1 keep waking them up but when they wake up, there's no work to do so they try to go back to sleep.
The standard deviation just below the real time Calculated multiplier (0.154) is a clear sign that the multiplier is not consistent across all 4 cores like you think it would be at full load. If Prime was running on both Dual Cores within the Quad, then it would drop to 0.000. There's a lot more going on inside CPUs than I imagined.
: What CPU did you kill and what did you do to kill it or is that a secret.
Edit: A smart bios would allow the two cores not working that hard to idle down like this:
The Core i7 works this way. All active cores run at the same multiplier but if a core enters the C3 or C6 state then it is considered inactive and unused cores are allowed to idle down. When you start overclocking, this can get screwed up depending on the motherboard.