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My host is a 64-bit ubuntu operating system and I want to setup a windows 7 virtual machine.

I suspect that using a 32-bit windows 7 vm does not have any benefits regarding the RAM and disk space usage in my case - as every 32-bit memory address of the VM would be mapped onto a 64-bit memory address of the host.

Is that correct and should I install a 64-bit vm instead?

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  • See this question superuser.com/questions/56540/32-bit-vs-64-dit-systems – Arye Eidelman Jun 22 '14 at 13:55
  • @743 Thanks you for that link. Unfortunately there is no explanation related to memory mapping of a 32-bit guest on a 64-bit host. I will improve my question. – king_julien Jun 22 '14 at 17:59
  • There is no relevant performance overhead. Other than a VM’s, of course. If you plan to assign less than 4 GiB of memory to your VM, use a 32-bit operating system in your VM. Simple as that. – Daniel B Jun 22 '14 at 22:34
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You should install 32-bit x86 version. The reason being, Windows 7 64-bit x64 requires minimum RAM of 2 GB to function properly. A 32-bit system in this case can function properly and pretty well on 2GB RAM.

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  • I understand this, however I expect that on a 64-bit host every 32-bit address of a VM will be mapped onto a 64-bit address of the host. This is just a hunch, if it's true that would negate my expected benefit. My question tries to get a technical confirmation for my hunch :) – king_julien Jun 22 '14 at 17:57
  • No, it doesn't work that way. There is no direct mapping between addresses in a VM and addresses in the host, whether or not the guest and host OS are the same bit width. Furthermore, with modern virtual machine monitors and CPUs that implement second-level address translation (SLAT), the "physical memory" seen by the guest OS is actually virtual memory as far as the host is concerned. ie each guest can re-use the same set of "guest physical addresses" and what each guest sees as "RAM" is mostly paged virtual memory in the host. – Jamie Hanrahan Sep 26 '17 at 22:18
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I think you should install the 64-bit version. I mean, if you use a 32-bit vm on a computher that is able to work with 64-bit, it is like if you had bought a Ferrari to drive at 20 mph. You're not getting the maximum performance level that the 64-bit system offers, because of the restrictions of the 32-bit vm you're using.

This might vary depending on the vm you're using, but I would recommend you to install the 64-bit vm, to ensure you take advantage of the benefits that the 64-bit technology provides you with.

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