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I'm not aware of a 32-bit type II virtualisation product for the Mac that allows a 64-bit OS to run as a 64-bit app.
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If you mean on a machine with a 32-bit OS, then again, it's not possible to run a 64-bit guest on a 32-bit OS without emulation (something would need to translate the 64-bit instructions into 32-bit instructions) unless either (a) the 32-bit OS allows 64-bit applications (like Mac OS X) or (b) you can bypass the OS with a hypervisor. If you mean hardware with a 32-bit processor that doesn't have 64-bit capabilities, then no, you can't do that through virtualisation - you would need an emulator rather than virtualisation and I'm not aware of one existing.
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Depends what you mean by a "32-bit host".
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