Real PDP11 model question

From: Jerome H. Fine <>
Date: Sun Sep 19 20:14:11 2004

>"Zane H. Healy" wrote:

> How big is a PDT-11/110? My PDT-11/150 is quite a bit larger than a
> DECmate III.

Jerome Fine replies:

I seem to remember that a DECmate III and the PRO350 are the
same size and even look similar??? Is this true?

> To the best of my knowledge the smallest possible PDP-11 made out of
> real hardware would be a 4-slot dual-height backplane, with a
> dual-height CPU (ideally a PDP-11/73), DLV-11J (providing console
> port), 3rd party disk controller w/bootstrap (preferably SCSI). That
> would leave room for one additional dual-height board. You'd have to
> figure out the power-supply and how to wire up any disk or tape
> drives. I'd build something like this, if I had the backplane, but I
> don't.

You seem to be missing MEMORY??? That would be the fourth dual
height board.

> The smallest DEC PDP-11 that I'm aware of is the PDP-11/03, but
> you've got to add a external drive of some sort.

As far as I understand, some backplanes that handle the PDP-11/03
can't handle the 11/23 or the 11/73. But some might be able to
handle all 3 CPU types. Are you aware of this problem and which
backplanes are in which category?

As for an external hard drive, for the VT103, even a 5 1/4" full
height hard drive can be placed under the tube - I have done
so VERY successfully, although a 3rd party disk controller
(dual RQD11-B from Sigma with onboard boot ROMs) was
required since an RQDX1,2 quad uses too much power and even
the RQDX3 has no boot ROMs.

> For people where a system the size of a BA23 is an issue, your best
> bet is going to be to simply run under emulation. In my case it
> isn't the size of the systems so much that is an issue, it's how much
> space all the documentation I have takes up.

Even for RT-11, the full set of DOCs is about as large as a VT100
and BA23 combined. And that is just the DOCs for RT-11 and
2 or 3 layered products like FORTRAN.

As you mention, I now rarely used the real PDP-11 hardware since
E11 run RT-11 at about 15 times the speed of a PDP-11/93 on a
750 MHz Pentium III under Windows 98 SE. Since I am an addict
for RT-11, where I run the software is not important. Having E11
is a GREAT improvement - THANK YOU John Wilson!!!!!!!!!

Using the emulation solution to run PDP-11 programs will mean,
at the very least, that software is just as important as the hardware.
BUT, be aware that it may be necessary to use SIMH in the
future since E11 is an x86 based solution, as far as I understand,
unless John Wilson ports E11 to a new platform.

Sincerely yours,

Jerome Fine
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Received on Sun Sep 19 2004 - 20:14:11 BST

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