I7-860 only 3 out of my 8 CPU threads

[senne]

Hello,

I have a system that worked well up untill now,
but then from one day on the other
I noticed a drastic performance decrease in games.

So after some testing I found out only 3 out of my 8 CPU threads
(so 2 cores out of 4 with one thread disabled on the second one)
are actually shown and being used.

This caused a bottleneck between the CPU and GPU.
And that's where the performance decrease comes from.

So the issue is known but the solution is yet to be found.
I have looked for settings in the BIOS but all my settings
were right and all cores were enabled, so was hyperthreading.

PC Specifications:

CPU - Intel Core I7 860 @ 2.8 Ghz (Stock)
GPU - AMD Radeon HD 7870
PSU - 750w
MOBO - Gigabyte GA-P55M-UD2

I have tried many things so far, including:

-BIOS Settings + Defaults
-Temperature monitoring
-Usage monitoring
-msconfig.exe settings
-stress testing

Any help would be greatly appreciated,
-Senne-

 

[ekoostik]

senne,
I just stumbled on this. Have you fixed this? I have the same CPU & motherboard. A few questions for you to get started:
What OS do you have?
What makes you say only 3 of your 8 CPU threads are being used? How do you know that?
Open msconfig, go to the Boot tab, then click Advanced options. In the "BOOT Advanced Options" window that opens, is Number of processors checked? If not, check it so that the dropdown beneath the checkbox is enabled. What options are available in the 'Number of processors' dropdown?
*Be sure to uncheck Number of processors before closing the window, or click Cancel to close Advanced Options and again to close system configuration.

Finally, have you done any work on your PC recently?