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Is it possible to run 64-bit guest OS (linux/BSD), using VirtualBox on 64-bit capable CPU, but when host OS is 32bit? (Host may be linux or windows.)

Will 64bit guest run at full speed or it will be slow (64-bit wide instructions emulated like in qemu)?

If 64bit guest will be full speed, is there some 64-bit microOS inside virtualbox? There should be 64-bit host OS to correctly switch between 32 and 64 bit code.

This question is raised because I want to run several virtualized 64-bit Oses and do a highload test between them.

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Why can't you run a 64 bit OS on the host? You can probably make it work, but you'll be severely restricted in a number of important ways (like the maximum memory available to each guest). –  womble Jul 6 '12 at 16:23
    
This just doesn't seem like a good idea, let alone I've never heard of it being possible, especially on VMware or MSFT. –  Brent Pabst Jul 6 '12 at 16:30
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When you typed in your question title millions of CPU cycles leapt into action to list for your personal selection a range of previously asked questions based on what you typed - you chose to ignore them all and the effort that went into allowing your that luxury, preferring instead to waste everyone's time. Shame on you. –  Chopper3 Jul 6 '12 at 16:37
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Chopper3, Can you provide a link to the related question? I can't find any question about 32bit host and 64bit virtualbox guest in this list (just rechecked). –  osgx Jul 6 '12 at 18:53

1 Answer 1

From the Virtualbox 2.1.2 User Guide, section 1.6:

64-bit guests

Starting with Version 2.0, VirtualBox also supports 64-bit guest operating systems.

Starting with Version 2.1, you can even run 64-bit guests on a 32-bit host operating system, so long as you have sufficient hardware.

In detail, 64-bit guests are supported under the following conditions:

  1. You need a 64-bit processor with hardware virtualization support (see chapter 1.2, Software vs. hardware virtualization (VT-x and AMD-V), page 10).

  2. You must enable hardware virtualization for the particular VM for which you want 64-bit support; software virtualization is not supported for 64-bit VMs. Note: On most systems, the hardware virtualization features first need to be enabled in the BIOS before VirtualBox can use them.

  3. If you want to use 64-bit guest support on a 32-bit host operating system, you must also select a 64-bit operating system for the particular VM. Since supporting 64 bits on 32-bit hosts incurs additional overhead, VirtualBox only enables this support upon explicit request.

On 64-bit hosts, 64-bit guest support is always enabled, so you can simply install a 64-bit operating system in the guest.

Still seems like a dumb idea.

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How big is the "additional overhead" from "3."? –  osgx Jul 6 '12 at 18:56
    
Variable. Like asking how many resources your OS uses. –  HopelessN00b Jul 6 '12 at 19:17

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