Hi All,
The Hybrid Lab was actually
half a flight down from the parking lot and had a PDP-9 interfaced to
an EAI 680 analog machine. Apparently the 9 could turn the pots
on the 680 which were designed to be turned by people. Since it
could turn them much more frequently than real people it was wearing
them out :-) The 680 was plug board programmed. The 9 had
DECTAPES and I still have one (the one "micro tape" I had originally
purchased from the CIT bookstore for the PDP-8 but then could never use
on it, as described on the web site) with PDP-9 FOCAL on it as well as
some FOCAL sources I wrote. Every time I would use the machine I
would finish by having PIP print a directory of what was then on the
tape to the 9's console. The last printed directory is still
folded up with the tape. Looking at this print out the tape also has a
copy of those two "music" paper tapes I had gotten from DECUS for the
PDP-9 as well as some other stuff.
73,
Chris Hausler |
I vaguely remember a
"hybrid computer", with an analog computer connected to a digital
computer. On the analog computer, differential equations could be
solved by including resistors, capacitors and inductors that were
"analogous" to the problem you wanted to solve. I seem to
remember the analog computer connected to a DEC PDP 9. I never
actually used the system, so I don't know exactly how it worked.
Just like I remember seeing the Athena, but never actually used
it. I do remember a BIC pen in the Athena's plotter. Really
classy, I thought.
Bob McFarland |
There is a photo of me in front that analog computer on the ASDG web
page. I remember it as being on the ground floor of Hamerschlag also.
As I recall, I never got it to do anything intelligent.
Mark |
Hi Mark,
That was the "other" analog
computer which occupied the Hybrid lab for a while, not the 680 which
was much smaller (actually smaller than the PDP-9 although not by
much). I know nothing further about it. I did have a 680
manual (about the size of a phone book) but threw it out about 5 years
ago (there is a limit to how much crap you can stuff into a small
bag. I keep testing this limit but every so often have to make
room for new crap ;-)
73,
Chris Hausler |
Dave Vavra was the sys programmer for the hybrid lab - when we hear from him, it should clear up some of the questions.
..ps08 |
The
analog computer that I played with didn't have any digital computer
interface. May have been an earlier one. We had some
simple analog computers in high school so I actually knew how to
program one. I remember Frank Caimi and I doing some stuff on it
to solve some lab problems.
Roy |
Hi All,
Again, the machine in the photo is not the EAI 680. See <http://archive.computerhistory.org/resources/text/EAI/EAI.680.1965.102646244.pdf> for
an advertising brochure showing pictures. It is advertised as a
hybrid computer in that it has digital interfaces specifically designed
for an external digital computer and refers to being ideal for new
university "hybrid" programs. Sound familiar. As you can
see from the photos in this document the 680 was programed on a plug
board. This allowed multiple users to wire up their experiment
and then take turns running it with other users without having to
un-wire between experiments. The unit in the web page photo is
not plug board programmable.
Also googling around I came
across a second analog computer web site. Going to its listings
for EAI it shows a number of "PACE" models and although not exactly
like the photo on the web site, damn close. So the machine in the
web site could be an EAI, just not the 680. The reference is
<http://dcoward.best.vwh.net/analog/eai.htm> If you go to
the home page for this museum it lists many analog computer
manufactures including Heath and analog computers tend to all have a
similar appearance, panels with lots of places to plug patch
cords. There are a number of other sites with even better photos
of the 680 than the above brochure, this all from typing "EAI 680" into
Google.
Weirdly, the business I just
retired from, automated railroad freight "hump" yards was done with
room sized analog computers from the early 50's up well into the
60's. To my knowledge the first digital computer yards were done
in the late 60's and I did my first one in 1973, but after a couple
more got into mass transit and didn't return to the hump yard business
until the early 90's. However we were still replacing old vacuum
tube analog computers at times (as well as two of those digital systems
I did in the early 70's, digital technology doesn't seem to last as
long ;-) I replaced my last large vacuum tube analog computer in
Indianapolis in 2004 and there is still a similar one running in
Buffalo, NY. This was to be the next one replaced and parts were
already being shipped to the site but last spring with the economy, the
railroad decided to not only terminate the upgrade project but to shut
down and abandon the yard. It is possible, however, that cooler
heads have prevailed. It was believed that if they ever turned
off the analog computer for any period of time, it would never run
again. Further, it is still maintained by an old guy who has been
with it for most of its existence and if they shut it down he would
retire and any knowledge of it would be lost. At least as of a
month or so ago, I heard the filaments are still lit :-)
73,
Chris Hausler |
I recall that we had the small desktop sized PACE TR-10 in room 55A. I never used it.
The larger machine was thought by a person from the Computer History
Museum to be a unit made by General Precision Systems (GPS). He noted
that the logo on the nameplate at the top of the unit looks a lot
like the unit that they show on their web site: http://www.computerhistory.org/collections/accession/X42.79
But I don't have any hints about the model number of the unit at CMU.
Was this older unit replaced by the hybrid computer?
Mark |
Hi Mark,
I believe the older analog
unit came after the Hybrid Lab (EAI 680, PDP-9) was set up (unless it
was hiding somewhere else around the campus and then was moved into the
Hybrid Lab). I don't believe it was there when I first started
using the PDP-9. I had assumed someone had cast it off and the EE
department snagged it (Williams again?). What with using the
PDP-9 I got interested in the EAI 680, got that manual I recently threw
out and sort of did a quickie do it yourself intro to analog
computing. With this, I drew up a very simple "toy" circuit to
wire as an introductory example but there were no plug boards for the
680 available to me, they were all in use by more "serious" users so I
never even got to try out my circuit. Thus my career as an analog
computer programmer was over before it began ;-)
Although I had come across
that old ads site before I hadn't spent a lot of time with it. I
see the tape drives on the G-20 were made by Potter. There's a
nice brochure about the Univac 1004 III showing the Uniservo VI tape
drive. I remember seeing one of those Minivac 601's for sale in a
local electronics store.
Regards,
Chris Hausler |
It turns out - none of the above - read more below....
rrr.org>
