The only reason I'm not using Hyper-V is because there are no guest drivers for Linux. Why can't VirtualBox see that VT-x is enabled on my computer? Microsoft's Hyper-V virtualization software can see this. It was installed in EFI mode, not legacy BIOS mode. My host operating system is 64-bit Windows 8. I'm trying to install Ubuntu Linux 12.10 so I can compile my own AOSP Android OS for my Nexus 4 phone. I have virtualization enabled in the motherboard's firmware. Unlike previous firmware versions this is a 100% UEFI compliant firmware from AMI and fully supports everything UEFI has to offer including Windows 8 secure boot (which is enabled). My motherboard is a Gigabyte GA-H77-D3SH with firmware version F8C. This is a quad core processor that supports Intel's VT-x virtualization. My computer has an Intel Core i5 3570K processor. The Acceleration tab is grayed out and I can't move the slider. It's preventing me from selecting more than 1 CPU for the guest OS. There is a major bug in VirtualBox 4.2.6.

Virtualbox 64 bit more than 1 core