XP 32-Bit Host 64-Bit Guest, >4GB RAM

[richwhitt]

I am new to virtualization.

I have XP PRO 32-bit and 64-bit. Currently, I am using the 32-bit version on my workstation because all of my hardware and software plays well with it and everything performs well.

My question is, if I use the 32-bit OS as the host OS, and the 64-bit as the guest, will the 64 bit guest OS recognize all the RAM I have installed in the system, or will it only recognize up to 4GB (the 32-bit limit)?

Should I use the 64-bit OS as the host for better performance?

[continuum]

Do you have more than 4 Gb of RAM AND all the drivers required for the XP 64 ?

If yes - I'd consider to use XP 64 as the host.

If not - XP 32 is fine

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[richwhitt]

I currently have 4GB installed but plan to install more. Just haven't done so because my performance on the 32-bit system is satisfactory. Now that I am trying to create a VM, I would like to go to 8GB.

The underlying reason for my question is that there are other users on this workstation and I would like to add the 64-bit VM to the current (32-bit) build to avoid disrupting the other users. But if the 64-bit guest won't be able to recognize all available resources then I guess I will have to.

My current build is very stable. Is it suggested that I do a fresh install for the Host OS anyway?

[continuum]

with 8 Gb RAM you should better use the XP 64 - otherwise the 8 GB RAM were wasted - as the 32bit XP can only access 3.2 - 3.8 Gb - depending on the board

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[richwhitt]

So if I have the 32-bit OS as the host, and the 64 bit OS as the guest, the guest OS will only recognize 3.8GB of RAM, even though more is installed. Correct?

[continuum]

Hmmm - not quite. You can not use the RAM above 4 GB - because the host can not handle it - but you still can assign more than 4 Gb for the XP-64 VM.

But this will be slow then as it must be swapped out ...

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[absynther]

64bit guest can only run on a 64bit host. 32bit guest can run on either as the bit boundry is only an issue going forward not backward. It's like a big bucket holding bits, can't pour 64ounces into a 32 ounce cup.

[continuum · Accepted solution]

absynther - so you say that the XP 64 VM that I am just running on my 2k3-32bit host is just my imagination ???

also the fact that I have assigned 6 Gb of RAM to it while my host only has 4 Gb and only detects 3.7 Gb of them - also imy imagination ???

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[ksc]

host OS != host processor. Only the host processor matters for running 64-bit guests.

To answer original question: guest can be configured with as much memory as you want. Maximum amount that can be used without swapping depends on how much memory the host OS can see; there is no point in adding more than 4GB to Windows XP.

[kernelphr34k]

Depending on the intended use of the OS you may want to move to a server OS for higher memory management.

http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

Good Luck!