System information:

Ubuntu SMP Thu Sep 16 16:05:42 UTC 2010 x86_64 GNU/Linux

Virtual Marchine:

VirtualBox 3.1.6_OSE r59338 linux.amd64

I wanna to install a virtual system with x86-64 in Virtual Box,But it seemed that it is impossible to do this.

The virtual machine tips me it only detected an i686 CPU.

Is there any link between the architecture of host and that of the client virtual OS?


INFO: Your CPU supports KVM extensions
INFO: /dev/kvm does not exist
HINT: sudo modprobe kvm_amd
KVM acceleration can NOT be used

sudo modprobe kvm_amdresult

FATAL: Error inserting kvm_amd (/lib/modules/2.6.32-24-server/kernel/arch/x86/kvm/kvm-amd.ko): Operation not supported


INFO: Your CPU supports KVM extensions
INFO: KVM is disabled by your BIOS
HINT: Enter your BIOS setup and enable Virtualization Technology (VT),  and then hard poweroff/poweron your system
KVM acceleration can NOT be used

But another problem happened,the VirtualBox displayed an error windows.:

VT-x/AMD-V hardware-acceleration has been enabled,but it is in the ineffective status. So the VirtualBox won't detect the CPU of 64bit,and fail to start.Please confirm the  support has been enabled.

How to check the CPU whether support the VT-x/AMD-Vtechnology?And start it in BIOS?But another Virtual OS (32bit)also enable this technology,and works well.


There is a link between the architecture of the host and the client, but only in so far that you can't run a 64-bit virtual machine on a 32-bit host machine.

  • 32-bit guest on 32-bit host should work
  • 64-bit guest on 32-bit host does not work
  • 32-bit guest on 64-bit host should work
  • 64-bit guest on 64-bit host should work

(By 32/64-bit host I mean the host machine CPU.)

To run a 64-bit guest, VirtualBox also requires hardware-virtualisation in the CPU (and not disabled in the BIOS!). To test for this, run kvm-ok in a terminal:

$ kvm-ok
INFO: Your CPU supports KVM extensions
INFO: /dev/kvm exists
KVM acceleration can be used

Only the first line is important here. (This tool is intended for use with kvm, but VirtualBox uses/needs the same hardware-virtualisation support.)

  • Jan, is there a setting which needs to be changed in order to get 64-bit guests to work? I can confirm this issue and I've been using VBox for ages. – Jeremy Oct 17 '10 at 2:32
  • It seems like to run 64-bit guests in VirtualBox you need a CPU that supports both 64-bit instructions and hardware-virtualisation. You can test if your CPU has hardware-virtualisation enabled by running kvm-ok in a terminal. – JanC Oct 17 '10 at 17:34
  • The kvm-specific part doesn't really matter for VirtualBox. – JanC Oct 17 '10 at 19:43
  • @Janc The result of kvm-ok has been added. – kit.yang Oct 18 '10 at 13:56
  • @kit.yang sudo modprobe kvm_amd in a terminal and again kvm-ok – hhlp Oct 18 '10 at 14:00

You can install 64bit on 32bit system, as long as your CPU is 64bit. I'm running a 64bit virtual machine on a 32bit Ubuntu with VMware Player without configuring anything. It seems to me that there is some issue with your VirtualBox. You are trying to install a 64bit client on a 64bit host using a 64bit VirtualBox, so it shouldn't give that error.

  • Well, qemu can run a 64-bit guest on a 32-bit host CPU, so there must be something wrong with VMware Player... ;-) – JanC Oct 17 '10 at 19:56
  • Well, in fact I never tried :) I just assumed it wasn't possible, because that is what I have read elsewhere. Do you know if VirtualBox can do that too? – lovinglinux Oct 17 '10 at 20:10
  • Qemu can use several types of emulation & virtualisation, and when required it can emulate a whole CPU + machine without virtualisation, even other architectures: ARM (e.g. Nokia n800 and such), MIPS, SPARC, PowerPC, etc. As stated in my main answer, VirtualBox requires a 64-bit CPU + hardware-virtualisation to run a 64-bit guest. – JanC Oct 18 '10 at 14:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.