Need a 64-bit guest (Ubuntu 12.04)

[scooter262]

I have a MacBook Pro and need to run a 64-bit version of Ubuntu. When I try to load the 64-bit image, I get an error: this kernel requires an x86-64 CPU, but only detected an i686 CPU.
Is there any way to run a 64-bit guest on my MacBook Pro?

[brycesteiner]

Is PAE enabled, VT-X/AMD-V

[Perryg]

PAE won't allow a 64 bit guest to boot in VirtualBox.
You need to start the Mac in 64-bit mode

[scooter262]

How do I start the mac in 64-bit mode?

[Perryg]

It should be holding the 6 and 4 keys down while you boot, if it supports 64-bit mode or you can look in your owners manual.

[brycesteiner]

The new Mac OSX defaults to 64 bit mode.

To see what bit mode you are in type in the terminal

uname -a

Does it say i386 or x86_64?

Perhaps it is the PAE selection

[Perryg]

@brycesteiner,
Do you know what PAE is/does?
This will not help hardware virtualization (VMX) and the way the guest connects to the CPU.

[brycesteiner]

PAE is a way for 32 bit systems to get around the 4GB limit.

I'm trying to say it could be a problem if enabled. I'm also saying that Mac OS X is 64 bit by default.

[Perryg]

OS X is an operating system the Macbook pro is hardware. The error is saying that it does not see 64-bit capability simple as that. Until VirtualBox can see the VMX portion of the CPU it will not be able to work for 64-bit guests. Since Mac's don't use bios they use the kernel. Since the OP is getting the error about being an i686 it has to be that they are using the 32-bit kernel. Look I don't make this stuff up just read what apple has to say about it. http://support.apple.com/kb/HT3773

[ChipMcK]

I'm also saying that Mac OS X is 64 bit by default.

Only if you are running Mountain Lion. Lion is 32 bit by default, unless . . .

as I recall, you need to boot while holding 6 and 4 on Lion

Check Activity Monitor (located in Utilities folder)
All Processes to see which mode the kernel is running