[Simh] VAX/VMS

[Johnny Billquist]

On 2016-02-16 16:54, lists at openmailbox.org wrote:
> On Tue, 16 Feb 2016 08:58:11 -0500
> Clem Cole <clemc at ccc.com> wrote:
>
>> As for what started this thread.   I think it is interesting that the long
>> term successful architectures in the market did have a excellent
>> compatibility stories. IBM with system 360 certainly set a high bar, and
>> DEC has nothing to be ashamed of, the different DEC lines, particularly
>> the Vax, did a great job here.    In truth, probably the best of pure
>> compatibility story has to be Intel.
>
> No offense, but to even suggest Intel has the best compatibility or that
> pure and Intel go together in the same sentence is completely over the top.
>  From every angle I can see, Intel has about the worst track record of
> upward or backward compatibility and the least amount of design integrity
> or purity of any vendor still in business and probably in the history of
> modern computing.

[...]

I think you need to keep the OS and the processor separate in this 
discussion.

As far as I'm aware, you can still boot an old version of MS-DOS on the 
latest x86-64 based PC you can grab. However, that demands not only that 
the CPU is backwards compatible (it is), but that you also have a BIOS 
that is compatible, since MS-DOS depends on that.

But there is no point ranting about the upgrades and enhancements to the 
CPU not being backward compatible. That would never be expected. The 
crucial question is if you can boot that old OS, and run your old 
programs. And the answer to that one is, I believe, yes.

	Johnny