[Simh] Compatibility you can use Was: VAX/VMS

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On Mon, 22 Feb 2016 11:13:37 -0000
"Dave Wade" <dave.g4ugm at gmail.com> wrote:

> > >
> > > You can't seriously mean that you think that a 32-bit application and
> > > a 64-bit application would be expected to be compatible with each
> > > other? I would expect the 32-bit code to work in 32-bit mode, but
> > > having it work if you are in 64-bit mode is a ridiculous expectation.
> > 
> > Really? It works fine on IBM's z/OS.
> > 
> > It seems ridiculous to me that you think it shouldn't. This is what I
> > have been saying. IBM moved from 24 bit to 31 bit to 64 bit and
> > everything still works. No expanded footprint, no duplicate libraries,
> > no problem.
> > 
> 
> That’s not (quite) true. As I said before problem state code works fine.

That is 99.9% of all applications code.

> Anything that uses supervisor mode will likely fail. 

Absolutely not true. I don't know of any code we wrote for XA and ESA that
runs sup state that had any problems going forward. We continue to support
ESA code to this day. I can't remember anything that failed. I also can't
remember an OS service that wasn't upward compatible.