[HECnet] Re: VSI VMS x86 on HECnet

What instructions did you have in mind? The reason I'm asking is because virtualization is a very old concept (in computer terms) dating to the late 1960's.  You don't actually need special instructions, just to handle a trap that would take you out of problem state (like doing I/O).  I /think/// you need the VM bit on x86 to handle real mode applications and operating systems (I.E., DOS) because you don't get the trap.  Was there something else? IBM enhanced their hardware to provide more support for virtualization and these are called LPAR's. The unreleased Jupiter instantiation of the PDP-10 architecture also had a VM bit; again, I /think/ to support user mode applications which expected unrestricted access to hardware. Tops-10 supports this and Tops-20 has a limited form of it (USRIO%).  In any event, it would have allowed you to boot Tops-20 under Tops-20, a fine concept. I don't recall that either the VAX or Alpha supported virtualization.  One imagines that perhaps this was thought unnecessary because the available internal instruction set simulators and the lowering cost of the hardware.