Setting up a VAXstation

Tim Shoppa shoppa_classiccmp at trailing-edge.com
Mon Oct 8 07:14:33 CDT 2007


Tony Duell said:
> I cna understnad why people are interested only in old software, not
> hardware, and want to run it under emulation on a modern machine
>
> My puzzlement is with people who want to run the old hardware (not have
> to run the old hardware becuase it is part of some machine tool or
> something) but don't want to understand what's going on inside. What more
> do you get over running the software under emulation?

In fact, availability of hardware is a huge factor in succesfully
making an emulator for a machine. All but the simplest processors
are complicated enough that there are little corner cases all over
the place where none of the processor/architecture documentation tells
you what is going to happen.

And outside the central processors, all peripherals but the very simplest
are filled with complicated and undocumented behavior.

Schematics could answer many of these questions, but in real life
they end up guiding the search for the answer to the question rather
than being the actual defining source for the answer.

So in general emulator users and especially developers completely
grok the need to have hardware working. Sometimes I believe that
today's emulator developers know much more about the architectures
than the original architects did :-). (In a couple cases, they are
the orignal architect!)

Availability of software is also important for making a reliable emulator.
You could spend years reading the books to write an emulator, but you
don't trust anything you've read or done until you've booted the simplest
OS.

Tim.



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