virtualbox.org

Just to clarify/confirm, can a Win 7 Guest VM only use the amount of memory that a Win XP Host can see?
Eg. - if a system actually had say 8+ GB, but XP can only see/use ~ 3.25 GB, is this all that a Win 7 Guest would be able to draw from?
Or is it possible for Win 7 VM to somehow use the extra memory that an XP Host can't see and isn't using?

The VM uses resources granted to it by the host, so yes, the VM can't use resource that the host doesn't know or can't/won't use.

And I'm sure you understand that, of that 3.25GB, you have to leave the host enough to work with as well. Ditto for CPU cores.

Hmm, too bad. Yes, I was aware that there needs to be enough memory left for the host, that it's essentially shared between the two.
Was just hoping that the VM may have been able to somehow see/use the extra RAM that XP Host couldn't see. Oh well.

Appreciate the prompt reply. Thanks mpack.

If you assign more than 50% of total RAM to the guest, you won't able to save state (It will be crashed with a VERR_MAP_FAILED). Even if you have a lot of memory (ex. 3GB) and the host is doing nothing else (host has 700-800MB free RAM, I would reallocate 400-500MB).

See #8630 bug ticket. (host WinXP, guest W7)