[Simh] VAX/VMS

[Patrick Finnegan]

On Wed, Feb 17, 2016 at 9:20 AM, Clem Cole <clemc at ccc.com> wrote:

> For whatever it is worth, this was a discussion about compatibility.  My
> point was and is, Intel owns the trademark; and defines / continues to
> extend the INTEL*64 and IA-32 ISA's.  The current definition can be found
> at:
>
> http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html
>
> Intel has invested heavily in the ability to moved customer codes from
> 4004 to today's Phi ISA and IMO, done an excellent job of it.   Certainly
> from the 386 family and later.  As Johnny and I both said, you can run
> MS-DOS and old DOS programs on my current system from an Edison (IoT)
> module that costs a few dollars all the way up to a world largest
> supercomputer (the Milky Way 2 system in China) - which is a bit of a
> frightening thought to me.
>
>
Can you run it on a Xeon Phi (eg, a 5110P coprocessor card)?


> So coming back to compatibility, when the first processors to support
> INTEL*64 were created, Intel's engineering team had a choice.   What is
> interesting is that Intel's engineers chose to ensure that current set of
> applications codes continued to run.   They did not have too.   We might
> have had two completely different instruction sets if they had chosen
> otherwise.  I personally think, we as consumers won because of that.
>
>
However, AMD developed and implemented the first 64-bit extensions to
Intel's 32-bit "x86" (Intel 32 if you prefer) instruction set.

Also, Intel (given a choice) had two incompatible instruction sets.  The
common 32-bit x86 ISA, and the Itanium 64-bit ISA.  I have several machines
with Intel's first 64-bit attempt at an instruction set in it (well,
actually the Itanium 2, but you get the idea).

Xeon Phi (as currently available) is also only *mostly* compatible with x86
code.  The difficulty I've had to get a standalone Linux kernel to compile
and run (or even build a working generic version of gcc for it) on the
31S1s that I've got at home are pretty good proof that it's not quite
backwards compatible... as noted in Intel's own documentation: "Knights
Corner is not completely binary compatible with any previous Intel
processor. " (
https://software.intel.com/en-us/blogs/2012/06/05/knights-corner-micro-architecture-support/
)

Pat
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