How to enable second physical cpu on hp xw8400 workstation running win 10 pro. ?

I have tried msconfig, which did not help. I have dual xeon x5355. I can see all 8 cores in device manager, but I only see 2 cores for one CPU in cpuz and task manager. The bios only lists one as well


I have updated my bios to the latest version. And even tried upgrading to windows 10 enterprise. Each cpu works as the system will boot with either one in the top slot.

Update 2:

Solved! Reinstalling windows fixed the problem.

3 Answers

  • 2 months ago
    Favorite Answer

    There are some solutions in these threads.

    Did you upgrade from Windows 10 Home to Pro? You might need to reinstall the OS if you did.

    The old Socket 771/775 series used a dual-CPU package for quad-cores like the q6600, q9650, Xeon x5450, etc. It would be for the best to test the 2nd CPU by itself to see if there's not a problem with the 2nd CPU package. With your dual-socket system, you are essentially running 4x CPU dies.

  • 2 months ago

    Besides BIOS update, you might need a different version of Windows.  Check if 10 Pro will do two processors.  Might need the Ultimate or Enterprise or server upgrade.

  • Anonymous
    2 months ago

    Make sure your BIOS is up to date.

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