Reproducing old machines with newer technology (Re: PDP-12 at the RICM)

Jay Jaeger cube1 at
Wed Jul 15 18:05:07 CDT 2015

On 7/15/2015 4:45 PM, Chuck Guzis wrote:

> On 07/15/2015 01:49 PM, Jay Jaeger wrote:
>> That would certainly be closer than any of the other examples that have
>> been thrown in the discussion.  But it, of course, is much newer than
>> the 1400 series.  IIRC, the discussion started when someone suggested
>> that there were quite a few machines that were similar to the 1400
>> series in terms of variable length.  Again, while that was true from the
>> perspective of variable length data fields, it wasn't from the
>> perspective of variable length instructions.
> Well, you do realize that I'm having fun with you? :)

Yes, it did kind of figure.  ;)  Or at least to be hoped.  ;)

> I've programmed the 1401--and while, not a 1410, it's not all that
> different.  I view it as an evolutionary dead-end, sort of like the
> 80s-90s Dataflow machines.  I suppose it what it was intended to
> do--provide an easy transition from stuff like the 407 accounting
> machine-unit record genre.  It was easy to program (heck, I still can
> recall a few opcodes).  I suspect that the real 1401 lasted as long as
> it did mostly because it was a way to perform spooling of input and
> output cheaply, where printing on-line with say, a 7090 would have been
> a waste of resources.  Better to write a tape and let the 1401 do it.

Certainly it was a dead end.   I suspect that the real 1401 (and its
compatible follow-ons) lasted as long as it did mostly because small
customers could afford the rent.  There weren't enough 7090 customers to
account for anywhere near the 1401 sales.

Certainly a lot of 7090/7094 series installations did do that - the
native printers, readers and punches for the 7090/7094 machines were
simply *awful*.

> My interest lies mostly in big iron and I"m not likely to see much of
> that in an FPGA implementation.  You have to admit that any hardware
> description that starts out with (page 1-2):
> "Cooling for the basic computer consists of two 30-ton water-cooled
> condensing units.  These units cool only the CPU, MCS and I/O sections.
>  The MCU is air-cooled.  With the optional memory, the basic computer
> requires and additional 30-ton condensing unit.

I've been amazed what people have worked into FPGAs.  You just never know.

As Gene Amdahl proved, with the right technology you didn't need all
that water (or worse) running around in pipes in your computer room.  :P

> Power for basic computer consists of one 250 kva 400 Hz motor-generator
> set.  The motor-generator set has the capability of providing power for
> the CPU, MCS, I/O and the MCU.  The optional memory requires the use of
> an additional 80 kva motor-generator set."

Loved those MG sets.  Our Amdahl's at WisDOT had them, and one could
hear the 400 Hz in the computer room.

In the basement of the U. Wisconsin CS building, I set up a 1410 that
had been donated by Oscar Mayer Co. - twice - and Paul Pierce, I and
another friend set up a 7094 II that had been at White Sands Missle
Range (WSMR).  The 7094 II took a hiatus when one of the bearings on the
motor decided it had fallen in love with the shaft, and became "one"
with it, resulting in the bearing's death, praying mantis style.  ;)   I
came down to the CS building basement one Sunday evening to find quite a
lot of smoke.  With the "project" having essentially no budget, it was a
while before the UW machine shop got around to taking the bearing off,
and a new bearing found and placed on the shaft.  After that, since we
had absolutely NO I/O devices whatsoever (aside from the 1410 console),
Paul adapted PUFFT (Purdue University Fast FORTRAN Translator) to do
RS-232 bit serial I/O through a sense switch, and I wrote a spooling
program that ran on a Datacraft 6024 located in the same room to do the
card reading and printing.  I suppose somewhere inside of it the DC 6024
was humiliated - I expect that it was much faster than the 7094 II.  ;)

(Now there is another candidate for an FPGA.  Just make sure you have
the fix in so that DMA doesn't stop during a Divide Immediate
instruction.  ;) ).  No software that I have seen for that one though.

> ...and whose 1980's final version was immersed in liquid nitrogen, does
> draw one's attention--and I will confess appeals to the "big boy toy"
> aspect buried in me.

Liquid nitrogen would be the "or worse" part.  ;)

> Still, there were some very notable machines from the aspect of
> architecture that would be worth resurrecting.  I'm just not sure that
> I'd consider the 1400 series to be one of them.

Worth/beauty/... are very much in the eye of the beholder.

I suggest that anyone resurrecting anything like this as an FPGA or an
emulator or a simulator is worth it for any number of reasons, even if
it never sees the light of day.  I applaud all of those efforts.  The
first one I became aware of was a PDP-10 FPGA implementation some years
ago.  Now there are many more.  A (presumably partial) catalog exists
(with quite a few broken links) at

> For example, I'd be interested in seeing, an FPGA version of a B5500--a
> remarkable machine architecturally if there ever was on.

Indeed.  That machine is also on my list, but I haven't seen logic
diagrams for it.  There is at least two emulators out their capable of
running the MCP and ALGOL that I am aware of, and another that runs in
Javascript of all things.  The latter is available at

(These pages also refer to the first one I had seen, done in in C++, by
Sid McHarg.  I have a copy, which probably isn't the most recent.  I am
not sure if he released it widely, or not).

Software is also available: (the "source").  Some
of that is also available at:

> Of course, suum cuique (your mileage may vary).
> --Chuck

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