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Re: Userland emulator

On 2013-03-25 23:27, Rhialto wrote:
On Mon 25 Mar 2013 at 20:10:18 +0100, Johnny Billquist wrote:
None, as far as I know. It was defined in VARM, but never
implemented. (But I might be wrong.)

What sort of special support would be needed? I know that x86 has
instructions which behave detectably different in user mode and
supervisor mode without trapping (which causes virtualisation to be
difficult) but I can't imagine that the VAX designers made the same
mistake. Even IBM 360 hardware can run VM (the operating system) under

The VVAX (Virtual VAX) addes three instructions (WAIT, PROBEVMR and PROBEVMW), adds one bit to the PSL (telling it's executing in virtual mode), and changes the behaviour of a lot of stuff if you are in virtual mode, as well as having a fake PSL for the virtual machine.


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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