Can't seem to use 2CPU on Oracle VM VirtualBox 5.0.2

Question

I have an Intel® Celeron® Processor N2815. I've confirmed Virtualization and VT-x are enabled.

I can't choose more than one CPU when configuring a Linux machine on VirtualBox; the scroller is grayed out.

Is there any way I can set it up with two CPUs?

Solution

As per the VirtualBox manual, you must enable I/O APIC to be able to assign multiple virtual CPUs.

You also need to make sure VT-x is enabled for that particular guest under the System→Acceleration tab. It is not enough to just enable VT-x on the host.

You also won't be able to edit the CPU count while the VM is running or has a saved state. Make sure it is in the "powered off" state.

Comments

[Admin]

Is there an option to use 2 cores instead of emulating two CPUs?

[Admin]

You only have one CPU. What you what is physically not possible. There is a difference between using multiple cores and multiple CPUs when creating a virtual machine.

[Admin]

@Ramhound As far as most software (and VirtualBox) is concerned, an additional core is functionally identical to an additional physical CPU. The only case where the distinction matters with conventional x86 hardware is when NUMA is involved, and VirtualBox doesn't care in the current version - it relies on the host OS to manage it. Even with VMware (which does care), you can emulate multiple virtual CPU packages on a single physical CPU package.

[Admin]

@Geruta VirtualBox only supports a single virtual CPU package with multiple cores.

[Admin]

Just my two cents: Have you rebooted after installing VBox? It happens that certain libraries are not properly loaded so only 32bit OS options are available at first but x64 OS (and multiple core adjustment) get enabled after rebooting IF virtualization settings are enabled on BIOS.

[Admin]

@Bob - It still remains. The user is attempting to use visualize multiple CPUs in a system that has single CPU.

[smith]

The acceleration tab is also grayed out.

[tvdo]

@smith Which specific machine is this? The motherboard model (or laptop model)? There's been reported issues with some Dell firmware. Also, do you have Hyper-V enabled? That will interfere with VBox's access to VT-x.