Windows 8 and 8.1 Forums


Can't set virtual machines to use hyper threading

  1. #1


    Posts : 4
    Windows 8.1

    Can't set virtual machines to use hyper threading


    Hello, 2 months ago I built a new machine with a Gigabyte Z97X Gaming 7 motherboard and Intel Core i7 4790K. It is running Windows 8.1.

    I have virtualization enabled in BIOS and Hyper-V disabled but, in some machines on VirtualBox or VMWare, i can't set it to use 8 cores instead the 4 physical ones. In other, it allows me to use it. At this time I could only set it to use 8 cores in a Windows 7 VM in VMWare.

    I checked CPU capabilities with coreinfo and it says Hypervisor is disabled and the other two options are OK.

    Did I forget to change some setting or something? I can't understand why sometimes work and sometimes not.



      My System SpecsSystem Spec

  2. #2


    Hafnarfjörður IS
    Posts : 4,376
    Linux Centos 7, W8.1, W7, W2K3 Server W10


    Hi there

    VMware Workstation 11 in the VMware settings for the VM you cans et the nr of processors - I think 32 is the max. !!! You don't need to set it in the Virtual (or HOST) Bios. Use the settings in the VM.

    Cheers
    jimbo
    Attached Thumbnails Attached Thumbnails cores.png  
      My System SpecsSystem Spec

  3. #3


    Posts : 1,875
    Windows 10 Pro Prieview x64


    For your processor the maximum number of cores you should assign is 3 (one less than the number of real cores in your processor). Most of the time though allocating only 1 core will be faster due to the overhead required to synchronise the assigned cores. If you assign more than 3 your VM will become unstable and freeze a lot. See https://forums.virtualbox.org/viewtopic.php?f=6&t=35256

    I run 8.1 Pro x64 in VBox and have 4 physical cores. I've found that it runs fastest (for me) with 1 core assigned - I've found adding more cores makes it slower.

    As for why you can't change it - what guest OSs are you running? Are they 32 bit or 64 bit?
      My System SpecsSystem Spec

  4. #4


    Posts : 4
    Windows 8.1


    Thanks for both replies, but I think you didn't understand well my question. I'm saying that in VMWare if I select 1 processor, I can't select 5-8 cores that my processor have. It only allows me to select 1-4.

    In VirtualBox, that thing is the same, but Virtualbox, when you go to Processors Tab, you can see how many cores it allows you to use in green, and up to 8 in red. If you select a number in red zone you get a warning saying you selected more cores that available ones.

    I other computers I had or I worked in, proccesors with HyperThreading and 8 total threads, shows up as 8 cores in VirutalBox. That's the difference with my computer. I attach a screenshot of that window.

    As for why you can't change it - what guest OSs are you running? Are they 32 bit or 64 bit?
    I tried it with different guests, all 64 bit. I have virtualization enabled on my BIOS, Hyper-V disabled on Windows 8 and VT-x enabled in all virtual machines with extended features.
    Attached Thumbnails Attached Thumbnails Captura de pantalla 2015-02-14 14.13.55.png  
      My System SpecsSystem Spec

  5. #5


    Posts : 1,875
    Windows 10 Pro Prieview x64


    Your processor has 4 physical cores ARK | Intel® Coreâ

    Hyperthreading doesn't count.
      My System SpecsSystem Spec

  6. #6


    Posts : 4
    Windows 8.1


    Thanks for replying.

    Yep, I know it is 4 physical cores, but as I said before, in some computer I saw virtualbox detects threads as cores.

    So is there a reason to virtualbox over a mac with I7-2600 works different? That computer is the other one I said before, where have 4 physical cores and 8 threads VirtualBox shows 8 cores as available. Maybe is the way how osx handle cores/threads that makes VirtualBox detect it as 8 cores.


    Can someone corroborate this?
      My System SpecsSystem Spec

  7. #7


    Posts : 1,875
    Windows 10 Pro Prieview x64


    I have a macbook with i5 3210M with 2 physical cores ARK | Intel® Coreâ

    I get the same issue as you - it counts the threads. VirtualBox gives me that message if I use more than 4. According to this support ticket it should be 2 https://www.virtualbox.org/ticket/12480 - supposedly they have fixed the retrieval of cores

    VirtualBox does not emulate hyperthreads but only physical cores.

    Certainly from their documentation you should base the number of processors assigned up to one less than the number of physical cores.
    Looks like a bug in VirtualBox - I get the same issue with VirtualBox version 4.3.22 released yesterday.

    Click image for larger version
      My System SpecsSystem Spec

  8. #8


    Posts : 4
    Windows 8.1


    The error seems to be on mac, not on my windows computer. I just checked the mac with updated version of VirtualBox and is the same. It shows 8 cores in green and 16 as max.


    Until now I didn't know which one was right, and how virtualbox takes threads.


    Thank you for helping
      My System SpecsSystem Spec

  9. #9


    Posts : 1,875
    Windows 10 Pro Prieview x64


    You're welcome. I'll report it as a bug over at VirtualBox.
      My System SpecsSystem Spec

Can't set virtual machines to use hyper threading
Related Threads
Hyper-V Virtual Switch 101: How to create and use Virtual Switches to connect Virtual Machines to Network I will try to make this tutorial as simple and easy to understand as possible. Therefore some examples used might seem to you fellow geeks too simple. However, I ask you to understand that...
Upgraded my win 7 pro that had virtual XP mode to win 8.1 pro. Everything from Win 7 came with it including my install programs. Noticed the virtual xp file .vmcx is there but can't access it. So I installed Hyper-V and got to the point of connecting to Virtual Hard Disk. Noticed it creats a .vhdx...
Hello all, I'm learning windows phone 8, and I want to run the windows phone 8 simulator on my PC ( OS windows 8.1 pro ), but the simulator can not run because it can not create the virtual switch in Hyper-V, and I also can not do it manually :mad:. This is the error when I create the new virtual...
Child monitoring with Virtual Machines in User Accounts and Family Safety
Okay, so I know that the Windows 8.1 child monitoring system allows you to see what apps are used and what webpages are accessed through a child account, but can it see through Virtual Machine systems such as VirtualBox? Please try to answer these questions in particular: -Can I see a webpage...
Virtual Machines in win 8 in Virtualization
Hi I would like to run ubuntu as virtual machine on my win 8 desktop pc. I installed vmware player and then separatley downloaded an ubuntu iso- couple of problems:- There seems no option on vmware player to create a VM VMware player doesn't seem to recognise iso files - its looking...
Eight Forums Android App Eight Forums IOS App Follow us on Facebook