[Discuss] VMWare Player question

[Richard Pieri]

On Oct 18, 2011, at 8:56 PM, Edward Ned Harvey wrote:
> 
> Nothing will support a 64bit guest on a 32bit host.

I digress here, because this is not strictly true.  IBM devised a method for running some 64-bit applications on 32-bit AIX servers.  I digress because this was not virtualization.  It was a clever use of a wrapper that mapped 64-bit functions to their 32-bit counterparts and then mapped the returns back as 64-bit data.  It was terribly slow, totally unsuited for production use.  IBM did it for developers to test their code given older hardware.

VMware could have made it happen.  Back before VT-x and AMD-V, VMware didn't really virtualize the x86.  VMware *emulated* the x86.  Ask Google about trap-and-emulate and why it doesn't work on the Intel architecture.  That's why-for the roughly 50% performance hit compared to what we have today with VT-x/AMD-V.  VMware could have incorporated AMD64 in their x86 emulator.  It would have been abominably slow, much like IBM's 64-bit to 32-bit mapping trick.  VT-x and AMD-V made this a non-issue.

--Rich P.