--- Patrick Finnegan <pat_at_purdueriots.com> wrote:
> Nope. VMS only runs on VAXen, Alphas, and (in the future perhaps)
> Itaniums...
I have seen information that demonstrates that the future is now. It's
not shipping, but it is real.
There was a contest (which I lost by several days :-( ) to guess when
OpenVMS on Itanium would be up far enough to get a directory. It was
months ago. There has been additional progress since then.
> While earlier versions of VMS might fit in the memory space of
> an 11/44...
VMS 3.x will run in a couple of MB of RAM. I've run up to 5.0 in 5MB,
but it wasn't pretty, and it only took a second user to thrash the
swapfile. We routinely ran VMS 4.x on an 8MB 11/750 with several
dozen users with only occasional discomfort.
> ...the instruction set is quit a bit more sparse (and quite a bit
> different... including 16bit words on the PDP vs 32bit words on the VAX)
Not to mention the 4-level protection model on the VAX vs 2 levels
on the PDP-11.
> I've heard you can get some PDP software to run on the VAX in
> 'emulation mode'
Emulation mode is only available on certain VAX processors - mostly
in the 11/7xx line. It is _not_ available in the MicroVAX line,
partially, I heard, because the engineering prototypes ran PDP-11
code faster than they ran VAX code. It was put into the first few
models because of all the RSX-11 code they could steal when there
wasn't enough native code to get real work done in development. The
"MCR" command is the (still working) vestigal invocation. In the
old days, on the right processor, you could kick off an RSX-11 task
with "MCR <taskname>". Now, it's just used to run (native-mode) system
utilities in SYS$SYSTEM (as in MCR AUTHORIZE or MCR SYSMAN).
> ...you most certainly can't go
> the other way around... at least without a lot of work and a big pile of
> crack to help with coming up with ideas :).
Big pile of crack indeed! You'd need enough to hallucinate that it was
working. You want a challenge? Port SIMH to the PDP-11. That'd be
about the best way to do it (and I don't think SIMH is going to like
being on a 16-bit processor, no matter how much memory you have).
> Oh yes, and don't forget you can run standalone things that don't
> require an OS, too. That's why they put those wonderful toggle
> switches on the front of the cPU :). Now I just
> wish I had a machine with some...
So does he... the 11/44 has a single switch. It, like so many PDP-11s,
uses "console-mode ODT" - you get a "_at_" prompt on the console terminal
and you type commands to enter words into core and execute code. It
is useful enough to manually enter bootstraps, but there's nothing to
look at. You need a pre-1980 PDP-11 to get blinkenlights (I'm still
hunting an affordable frontpanel for my 11/70...)
-ethan
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Received on Wed May 21 2003 - 09:55:00 BST