Ethan Dicks ethan.dicks at
Wed May 1 17:30:41 CDT 2019

On Wed, May 1, 2019 at 2:54 PM Antonio Carlini via cctalk
<cctalk at> wrote:
> I may have missed some of the thread, so this might be old news ...

We've tossed around the facts from the edges but didn't list them one by one.

> So I think that to use anything pre-V4.0 you need compatibility mode
> support in SIMH. But that seems to be there.

I think that's true.  MicroVMS 4.0 runs on MicroVAXen, which don't
happen to have compatibility mode, so I think it's safe to say that it
was all worked out by then.  I'm pretty sure there was still some
PDP-11 code in the corners of late v3.x.

> I would expect V1.x to feel distinctly clunky in comparison ... to V4.x
> and later.

I would agree (I got started with V3.4 or so, so anything V2.0 or
older is going to feel strange to me, I'm sure).

> Still a fun exercise though I would think.

No doubt.  Definitely a learning experience.

I was just a user for V3.x, then became a System Manager with V4.x
(late 1985 or early 1986), then started doing device drivers in 1988
with the push to add SMP under V5.0, at first driver upgrades, then
later, drivers from scratch.  How many times a day can you crash a
VAX?  Lots.


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