PolRoger: Thanks for posting your tests.
MSR 0x198 used to contain the VID voltage in the Core 2 design. Intel got rid of that information in this register when they switched to Nehalem Core i7. With Sandy Bridge, this information has been returned to this register.
Edit: My best guess it that the number that RealTemp and Core Temp reports is a VID request voltage and the voltage reported by CPU-Z is actual core voltage.
Here's what the Intel docs say.
RealTemp uses the Intel approved method as outlined in their November 2008 Turbo White Paper and accurately tracks the average multiplier. With the previous processors, CPU-Z decided to report a consistent multiplier at idle for validation purposes. This didn't always accurately report what the CPU was doing internally but I can understand his reason for doing this. I'm not sure if Intel encouraged this decision or not or how he has decided to report Sandy Bridge.
Anyway, RealTemp tells it like it is. If it shows a wandering multiplier at idle it's because various C-States are being used. I'm not sure if it is possible to get a nice steady multiplier in Sandy Bridge when the CPU is idle. Turbo boost depends on individual cores being able to enter the deeper sleep states like C3/C6. If you disable all of the necessary C-States, it might prevent turbo boost from working properly. Sandy Bridge CPUs depend on turbo boost to obtain multipliers like 45.
The reason RealTemp 3.60 was showing a zero multiplier is because you likely have one or more monitoring programs on your computer that are misusing the shared system performance timers. AIDA64 / Everest was causing problems by resetting and stopping and starting the shared timers so with RealTemp 3.65, I switched to a different set of timers that hopefully are not being abused like this so the reported data should be very accurate. This is also very likely the same reason why Core Temp is not reporting the multiplier correctly. Other monitoring programs are not treating the shared timers within the CPU as a shared resource.
Does RealTemp 3.65 allow you to overclock and adjust your multiplier from within Windows? You need to turn on at least one temperature icon and then have a look at the system tray menu that pops up. You should be able to find an option for this. I'm just checking to see if it works.