Sandy bridge CPU i72600k only using 3cores (6 threads)

[ces160]

Hi all,

I'm in need of a little help.

I have an i7 2600k and I'm using a Asus P8Z68 Deluxe Gen3 motherboard.

The CPU is (well was) over clocked to 4.6 Jiggahertz. My temperatures were reasonable with a H100, Max core temp 77 degrees at full load (CPU plus two 680 burn in for 16 hours).

Everything was working exactly the way I wanted it TO for a few months.

Last night I opened up CPU I'd to check the voltage and clock speeds and noticed that the CPU was not turboing up to 4.6 but rather pegging at stock 3.4 Jiggahertz. I than noticed that CPU Id was indicating that there was only three cores and six threads.

I went into the bios and had a look to make sure all cores were enabled and they were all at the same clock. Everything was they way I left it, nothing had changed. I loaded optimised defaults and restarted. CPU Id is still only indicating three cores and six threads.

Any one have any idea what happening?

[winny3141]

What operating system are you using? Because in windows 8, the kernel tends to "park" or disable certain CPU cores it feels are not in use in order to preserve power.

 

- winny3141 :D

[Sundanc3]

You can check how many cores that are selected to be "active" in the BIOS. Just make sure they are all turned on. 

[ces160]

Hi all,

 

Thanks for the replies.

 

I'm using windows 7

 

I have already checked the bios and made sure that all cores are on.

 

I'm really hoping its not dead. I was not planing on upgrading to Haswell. 

[SkilledRebuilds]

NOTE: This will force the OS to reset the count to default for the amount of Cores you now have.

http://answers.microsoft.com/en-us/windows/forum/windows_7-hardware/howto-get-windows-7-to-detect-your-new-multi-core/71519d51-f6cb-47df-b3ff-66c2928d6de4

The link contains the information below, and moreso, I recommend reading it.

Let me give an example:
You install Windows 7 with a dual-core processor and have this option checked for "Number of Processors" (in Msconfig > Boot > Advanced options) and the amount set to "2" (for dual core). This setting is not mandatory to be set but some ppl do in order to force Task Manager to show 2 graphs (or 3). One graph for each processor. At a later point in time you upgrade to a Quad-core or Tri-Core processor. The OS will not read this extra core or have anything enabled to physically use this extra core(s) until the following are performed:

1) Uncheck in MSConfig > Boot tab > Advanced Options > "Number of Processors" and exit MSConfig

2) d/l and install an applet called EasyBCD 1.7.2 (or later, Google: EasyBCD) which supports many features of Windows 7.

3) Go into Advanced Options in EasyBCD and select "Limit Widows to '0' CPUs (Leave 0 to reset)". Click "Apply Settings" and exit EasyBCD.

NOTE: This will force the OS to reset the count to default for the amount of Cores you now have. There is possibly a boot setting that can be added that I may not be aware of to do this same function but this little applet works and does the same thing. Don't muck around with any other setting in this utility if you don't know what you are doing it may leave your computer unbootable and a complete reinstall or long repair may need to be performed. Just make sure this one setting is set to "0"

4) Completely shutdown the OS (not reboot or restart or logout). Correctly Shutdown you computer so the it powers down.

5) upon restart into the OS the Task Manager > Performance tab should now show the correct amount of per core graphs if you have the "One Graph per CPU" option selected. Yay your back in business =)

[ces160]

Thanks everyone for the help.

 

To fix it i went to msconfig > Boot > Advanced options > Check the Number of processors box and set to 1 ( the max i had was 6) > restart. on boot task manager indicated only one core was being used. 

 

i than went back to msconfig > Boot > Advanced options > un checked the number of processors box and restarted. On boot all 4 cores and 8 threads were back.

 

I have no idea what happened or why windows decided to turn off one of the cores. To stop it from happening again i went back to the options, checked the numnber of processors box and manually set it to 8.

 

This has seemed to fix the issue for now. If anything changes will let yall know. 

 

Thanks again to every one who posted a reply. 

[SkilledRebuilds]

Glad you got it sorted in a quickly fashion, I should have probably just posted that you do what you did, but I did not know your PC knowledge so thought the above instructions would suffice :)