Only one core detected (on my dual core) in CPU-Z/Core Temp/Prime95etc

So I just did a little overclocking at settings I'm fairly sure are stable (don't remember how long I ran prime95 then but I think several hours - about 6 hours today yields no errors), but I notice everything is saying I only have one core.

I never thought to check this or knew it was supposed to show multiple but I see in task manager -> performance, there is only one graph of CPU usage. I'm pretty sure it was this way since I got it so I never thought anything was wrong.
CPU-Z detects it as the correct processor - Core 2 Duo E8400, but on the bottom right shows 'cores - 1, thread - 1'.

Prime 95 defaults to bringing up 1 worker in a pretty recent version (25.9.4.0) which it's supposed to automatically detect multiple. Looking back, I remember multiple workers were opened before by default.

Is overclocking causing one of my processors to shut down/not register?
Default speed of the processor is 3.0 ghz, overclocked to 3.825 ghz currently.
Vcore is showing 1.320 V in CPU-Z (set to 1.35625 in BIOS).
All other voltages left at auto/default, RAM at rated 2.1 V.
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More about only core detected dual core core temp prime95etc
  1. Check BIOS and MSCONFIG for options that limit the number of cores being used.
  2. Yeah that's odd. Should be 2 cores 4 threads.
    Sounds like something is turned off, like what Twoboxer says.

    If you disabled things in your CPU settings in the BIOS as well, I'd go check you know what was disabled (if thats the case).

    I'm also assuming you're not using the factory heatsink, and that' you've tried lowering your clock speed and seeing if that helps?
  3. Twoboxer said:
    Check BIOS and MSCONFIG for options that limit the number of cores being used.


    alright, what might these options look like? I don't have much of a clue what to look for.

    There are several enable/disable options in the BIOS I haven't figured out but I'm pretty sure I never messed with those.
  4. SpidersWeb said:
    Yeah that's odd. Should be 2 cores 4 threads.
    Sounds like something is turned off, like what Twoboxer says.

    If you disabled things in your CPU settings in the BIOS as well, I'd go check you know what was disabled (if thats the case).

    I'm also assuming you're not using the factory heatsink, and that' you've tried lowering your clock speed and seeing if that helps?


    I don't think I disabled anything that wasn't already but could be wrong. Would the factory default possibly have this disabled? I wouldn't think so since the board is definitely among the 'dual core era' - eVga 750i FTW. Has the default phoenix BIOS, whatever version, not sure.

    I use a Xigmatek 'HDT' cooler, which some reviews pointed to as the best of the best. It was a bit of a challenge to try and get the coolant applied correctly but I think it did it decent. I've been running this CPU/MB since may 08, so I don't think it's any obvious hardware problem like that, seems likely a setting somehow.

    Any help on what options control those settings would be appreciated.
  5. I see one option that could mean something but not sure - MPS control for OS.
    'Use this function to select the Multi-processor Specifications (MPS) version that BIOS passes to the operating system.'

    Shows '1.4' in the example picture though.

    From reading a thread elsewhere, sounds like it's a problem with XP detecting that the processor is multi-core during install, and apparently theres nothing to be done other than reinstall the OS, possibly repair.
    What I'd like to know then is - am I actually using both cores when I game or run multiple apps, or is one core totally out of use?

    Intel's processor ID Utility does indeed pick up 2 cores (but CPU-Z still doesn't).
  6. I don't see how you could be using two cores when Prime95 and Task Manager think there's only one core.

    1.4 prolly means "1 thru 4". I guess you hit enter, see what it says, and pick a new option if necessary.
  7. I switched the option over to 1.4 - it didn't change anything.
    I haven't gotten around to formatting or setting up a boot partition on another drive (what I plan on) but I'm assuming that's the only way to fix it.
  8. Long shot but try "Start Menu/Run/msconfig"

    Boot.ini tab, click "Advanced Options".

    Nothing should be checked.
  9. yup, they're all unchecked.
  10. What motherboard and BIOS are you using?

    Was this a completely new build? Or was the E8400 dropped into a previously single-core system?
  11. Tried clearing CMOS?
  12. Twoboxer said:
    What motherboard and BIOS are you using?

    Was this a completely new build? Or was the E8400 dropped into a previously single-core system?


    Mobo is an eVGA 750i FTW, BIOS is whatever comes with that stock - phoenix something or other.

    On a fresh install of XP, 2 cores were picked up instantly in task manager. However now I can't get internet to work for some reason on that new copy of XP.
    So that definitely indicates to me it's just an error with windows' install process.
  13. @Twoboxer your msconfig and bios suggestion solved my problem. i have a core i7 and cpu-z was only showing 1 processor and 1 thread. so i looked into msconfig and in the boot tab there are advance option in that i have selected 1 processor so that was my problem. so may be original poster can look in to that..

    thanks again twoboxer
  14. Unfortunately, he says he did that.
  15. I have a similar problem.

    When i first bought a new system a couple of years ago (e6300, msi P965neo), everything installed fine, both cores were running and recognised.

    After i first reformatted the system, it only detected one core. At the time i didnt really care, it wasnt stopping me from playing the games i wanted to play, and i thought that it would fix itself when i did my next reformat.

    Since then ive reformatted multiple times, legit copies of xp home and professional, and i tried a less savoury version as well, and eachtime it would not recognise the second core. Bad company 2 beta started this morning and i need that second core now.

    Firstly, in task manager, there is only one core recognised. I have no option to select "one graph, multiple cpus".

    Secondly, in device manager, it does infact show two cores, this is what i found wierd.

    Thirdly, in msconfig, i am unable to force NUMPROC to anything other than 1.

    I have gone thru bios and there doesnt even seem to be an setting to either disable or enable multiple processors, unless it is some wierd acronym.

    Short of throwing the prick out the window and buying a new comp, i dont know what to do. ANY help will be appreciated, even if its bad news. come forth thy savior
  16. I've since started using win 7 - it detects both cores.
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