Strange multiplier fluctuation (2600K @ 5GHz)

[niemion]

When under load the reported multiplier of my 2600K in CPU-Z will vary between 47 and 48 (some times all the way down to 42). This is with all power saving features disabled, but the result is the same with them enabled.

Reducing the worker count in a Prime95 blend session, to three, two or one, will fix the problem, and CPU-Z will show a multiplier of 50. This is equivalent of setting a lower core number in the BIOS which has the same effect.

Any suggestions? (Power supply is a Corsair 850AX, see all hardware specs in profile)

http://www.youtube.com/watch?v=s-Xu7OpwfcQ


ASRock Z68 Pro3 (Bios ver. 1.30)

Intel Speedstep [Disabled]
Hyper Threading [Disabled]
Active Processor Cores [All]
Enhanced Halt State (C1E) [Disabled]
CPU C3 State Support [Disabled]
CPU C6 State Support [Disabled]
Package C State Support [Disabled]
CPU Thermal Throtling [Disabled]

Software used

CPU-Z 1.57.1
AIDA64 1.70.1431 Beta
Real Temp 3.67
Prime96 26.6 build 3

[Falkentyne]

You should increase the current and watts limit.
You shouldn't need to do that, though, if you are using a global multiplier, so that only the BIOS can control the cores, instead of being able to adjust the multipiler in the OS. I think most of the problems with downclocks like this happen when people have OS multiplier control enabled, and set the turbo multipliers for each core. Could be wrong, though.

[niemion]

I'm using a fixed multiplier at 50 set in the BIOS. I have uninstalled the OS overclocking software since it's silly and slightly buggy.

How would I go about changing the current and watts limit?

[CrazyNutz]

I'm seeing this happen on my 2500k, and MSI P67a-gd65. I haven't been able to solve it yet I think it started after I updated to a newer bios, as I did not notice it happening on the original bios.