[Info-vax] OpenVMS.Org quick pool

[Stephen Hoffman]

On 2012-08-18 02:04:00 +0000, John E. Malmberg said:

> On 8/17/2012 10:31 AM, Keith Parris wrote:
>> 
>> 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.
> 
> 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.
> 
> There is a simpler (relatively) way:

Or if you have source code, port the Itanium application code back to 
Alpha, and emulate that.

> 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.

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.

-- 
Pure Personal Opinion | HoffmanLabs LLC