[Info-vax] OpenVMS.Org quick pool

[John Wallace]

On Aug 18, 1:03 pm, Stephen Hoffman <seaoh... at hoffmanlabs.invalid>
wrote:
> On 2012-08-18 02:04:00 +0000, John E. Malmberg said:
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> > On 8/17/2012 10:31 AM, Keith Parris wrote:
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> >> I'm not privy to any plans, but thinking in terms of what's technically
> >> possible: Consider what you would have it you took the Ski Itanium CPU
> >> emulator (which lacks emulation of any platform hardware) and added
> >> enough code from HP VM to provide a platform environment which looks
> >> just like HP VM to the VMS instance inside (with the HP VM code adjusted
> >> for endian-ness, and to run on Linux instead of HP-UX). No changes would
> >> be required in OpenVMS I64 code for it to run inside such an environment.
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> > The Ski emulator would only be needed if the HP VM was not running on
> > Itanium.  And the HP VM would not still not provide what was needed.
> > The SKI emulator would have to be further enhanced.  Based on the
> > description on the project page, the SKI emulator appears to be only
> > emulating the user mode instructions, not the stuff needed for the VMS
> > kernel to run.  That would be way too much work.
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> > There is a simpler (relatively) way:
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> Or if you have source code, port the Itanium application code back to
> Alpha, and emulate that.
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> > Now the literature for some of the advanced emulators are caching some
> > translated Alpha/VAX code with native code to get the speed up, so
> > commonly used sections of VMS would be effectively running in x86 mode.
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> That's fairly common with a JIT design.  LLVM has tools for building
> this, and there's LuaJIT which does this, and there's (of course) Java
> and its JIT.
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> --
> Pure Personal Opinion | HoffmanLabs LLC

I don't know if QEMU pioneered JIT translation/compilation/caching in
emulators/simulators/virtualizers (didn't FX!32 do that kind of thing
anyway) but there are writeups that imply it did. It's really quite
clever (from what I've read) anyway.