Restoring a DEC 340 Monitor | Hacker News Reader

Restoring a DEC 340 Monitor

engblg.livingcomputers.org

63 pointslarsbrinkhoff27 comments

Damn, that circular screen reminds me of the computer on the old Star Trek episode "Assignment: Earth".

This is where the Enterprise goes back in time to a 1960's Apollo launch. They then encounter a man from the distant future, "Gary Seven", who also traveled back in time.

Gary Seven had a computer that looked like DEC 340 (https://www.pinterest.com/will5967/sci-fi-star-trek-tos-s02e...).

This episode also has a very young Teri Garr as his secretary and a cat that turns into a woman with cat ears.

The M5 developed by Dr. Daystrom had the same circular display.

For those unfamiliar with the organization at work here, the Living Computer Museum is a gem of a museum located just south of Downtown Seattle. It’s chock full of amazing historical computers that you can actually use for the most part.

I’ve been to the museum probably a half dozen times since I discovered it two or three years ago. Each time I come back there’s something new on display. Highly recommended.

I love this place--it's one of my family's go-to destinations when the weather's crappy. They have a terrific exhibit right now where they recreated 1980's arcade--got the second highest score on the Centipede cabinet after a 30 year hiatus.

Its really sad they don't have any that allow you to use a front panel. Even their IMSAI 8080 has a plexiglass cover over the switches.

I understand why they do it, but I think front panel computing is something that will be lost without letting a new generation experience it. Its a much more direct way to experience the machine.

Other than that complaint it truly is a great museum. They even have a Xerox Alto you can play with.

I wonder if a front panel could be developed to work in conjunction with an emulator. As it was explained to me, the few systems that you can’t play with are mostly because they’re easy to mess up and hard to reset.

It sounds like you have some expertise in front panel operations? If you have the time and inclination, maybe you could offer to help them out. At the very least, an email explaining your thoughts might inspire one of their engineers to create something.

There are cheaper kit clones of the Altair and others with front panel switches.

I just find it weird that they don't let you touch the one thing that can't be emulated well, given the mission of the museum.

In the 90s, there was a computer junk store south of the international district (just south of I90) in a strange industrial location that actually had a Xerox Alto for sale (among many other interesting things). Makes me wonder if the locations are related.

Nice place to stock up on model M’s, at least. I miss those times. I once found an old Sun desk side computer for sale at a similar store in Bellevue. Radiation hardened with a SCSI drive that was even bigger (desk side units are about the size of a filing cabinet).

It's a different beast, but I would love to know how the CDC-6600 dual screen console was controlled. I have no idea whether it had internal memory to keep a character-based display list or whether all tracing was controlled from the host computer. Does anyone have anything on it?

http://ed-thelen.org/comp-hist/vs-cdc-6600.html#S-P-Hardware

Search for "Characters on the monitor", seems to be software based vector display.

I enjoyed this quote from the above link:

---

I have a story about Real Time Systems design that my supervisor told me years ago:

At a presentation on Real Time System design methodologies, during the question and answer period one person complimented the presenter on their talk and methodology but commented that it did not seem to be able to specify adequately the Real Time constraints, especially in their specific application.

So the presenter asked what was their application and assured them that it should only need minor changes to handle whatever made the application special.

The questioner then explained "Our application collects data and then transmits the data to another computer for storage and later analysis. The computer that our application runs on is attached to one end of a one meter long steel rod, the other end of this rod is attached to a nuclear bomb that is about to be detonated in a test. If the application has not completed all its tasks before the blast wave destroys the computer then it fails to meet its requirements. How would this time constraint be shown using your methodology?"

The presenter replied "Oh, I'd never thought of that..."

My supervisor then commented: "That is the difference between Soft Real Time Systems and Hard Real Time Systems".

In case someone else is interesting in the font used for the console, http://bitsavers.trailing-edge.com/pdf/cdc/cyber/cyber_70/fi... has that information. I spent a long time looking for it (and I think I read all the documents on the site, EXCEPT FOR THIS ONE #@⁾

It's a big, high-power analog monster, controlled by the Peripheral Processor (PP) that it's connected to. The PP holds the display list in its small local memory and refreshes the console tubes constantly. They have long-persistence phosphor but still flicker.

Recently there was a thread on that topic on the TUHS mailing list - including a story about exploding one :-)

I misread the title and initially thought that it would be about the DEC VT340, a graphics terminal that I used a lot back in the 80s. Interesting that product numbers were reused.

> Interesting that product numbers were reused.

When you're in business as long as DEC was, I think that inevitable if you want the product numbers to be short and memorable.

I made a more detailed title, but someone changed it to the title of the blog post.

It's not a VT series terminal, but a Type 340 CRT vector display. The "Type" designations were used with early DEC products.

Quite likely Germanium transistors can be replaced with their relatively inexpensive Soviet NOS copies. Many types were manufactured well into 1990s.

This is a great museum, I've been a bunch. They really have an amazing collection.

Last I went I actually talked with Keith and some other of their people who are restoring all kinds of stuff. They're very interesting people to talk to. I highly recommend visiting and asking around if you're in downtown Seattle some time with a free afternoon.

Is there a reason a Silicon transistor/diode wouldn't work here? I'm assuming it either has something to do with voltage sensitivity or frequency, but older computers like this tended to use fairly high (TTL) logic for signaling.

> Diodes this old when put on a curve tracer can sometimes look more like a resistor than a diode.

Ah, ok I get it now. My eyes somehow completely skipped that paragraph.

Brother, this system predates the concept of TTL by quite a fair margin.

I will proudly confess I am not well versed on the history of EE :)

Looking forward to see these PDP-6 or PDP-10 applications:

* TECO

* DDT

* Spacewar

* Dazzle Dart

* Game of Life

* MacHack VI

* Stanford University Drawing System

* SHRDLU

* Logo turtle graphics

You can see Spacewar (and if you get into the demo room well before the demo starts, even play it) at the CHM in Mountain View, CA. The PDP-1 demo (with music synthesis and spacewar) is on first and third Saturdays, 2:30 and 3:15p [1]. But the demo room is ridiculously small and crowded, so be early.

[1] http://www.computerhistory.org/hours/

It'd be interesting to compare PDP-1 and PDP-10 Spacewar side by side.

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