[Info-vax] VMS internals design, was: Re: BASIC and AST routines

[Arne Vajhøj]

On 11/26/2021 9:12 AM, Clair Grant wrote:
> Have not been here for a bit. My answer to the "how many people"
> question.......
> 
> If you include the compiler teams who were actually separate from VMS
> Engineering itself in the bad old days, there was somewhere in the
> range of 250 people in the two organizations combined when we ported
> from VAX to Alpha and then Alpha to IPF. Not all of these people
> worked on the port all at once but they were all available to pitch
> in as needed even when it was not their full-time job. Both of those
> ports took 3 years; they were very different technically but
> nonetheless, the total elapsed time was eerily the same.
> 
> With the same person power, porting to x86 would have been roughly
> the same, I believe. No reason to think otherwise (similar issues,
> same parts of the system needing architecture-specific work). But
> that is not the case. We have way fewer people now so it is not
> surprising to me, at least, that it is taking way longer.

People without experience in big software projects tend to think
that it is a few hard to solve problems that take the time. But
that is rarely the case. The time is typical spent on relative
easy problems - there are just a lot of them. I do not expect
the fact that x86-64 is 2 mode instead of 4 modes, the fact
that lot of VMS code is Macro-32 or Bliss to be what is driving
the effort required. But you have N places where there are something
ISA specific. And N is a large number. And for every one of those
somebody needs to understand the problem, make the fix, document it and
test it. It takes 1 day or 1 week or 1 month. But multiply that with
thousands of places. And then mix in the hassle of cross-developing on
a different platform, the coordination effort to ensure that all parts
are changed in a compatible way and the interruptions of 8.4 support
and requests for new features / bug fixes from customers and
the man months start going quickly.

Arne