Digital Equipment Corporation (DEC) PDP-1 Computer System Information

Source Documents

The following records are a very incomplete listing selected from the available correspondence, letters, memoranda and reports published by the Computer History Museum. Refer to their Collections and contents for the complete records. The references below may only contain the title or a brief summary of a Memoranda's contents. A subset will contain an extract of a memoranda, and rarely, some will have nearly most of a record. Do not rely on any of the information below, always refer to the source material published by the Computer History Museum. The listings below are only a fraction of the material published by the Computer History Museum. Any copyright of the Computer History Museum remains with the Computer Museum.

DEC records are not organised as a single stream organised into a simple timeline but consists of multiple batches of records in multiple, ovelapping, forward or reversed timelines. There can be multiple copies of a record in different batches. A single batch can appear in different subsets of the DEC Collection. The following was selected to trace the history and produce a timeline for the PDP-1. Other records are included purely out of curiosity, or a whim. You have been warned.

Date December 10, 1959

From Ken Olsen

David Caldwell from the Physics Department of MIT called and wanted information about 18 digit and our 36 digit computer. They have some Air Force money that they can spend on this sort of project. They would like to have zero but would like more precision on the oscilloscope than 9 digits would, and they would like more computing speed because right now they have to read information off and put it into the 704. They like the machine particularly for their atomic trace studies but would also like to use it for regular computation within the physics Department. They are having a meeting today and that was why he was gathering the information together right now.

I invited him out here to see the machine and told him that it's possible we could even bring it down there and plug it in his wall and give it a try there.

Date December 11, 1959

Bi-Weekly Report

From Ken Olsen

PDP-1 Terminal Equipment

The Flexowriter fell flat on its face during the EJCC, and we cannot tolerate it from now on. For a tape reader, we are considering the Digitronics photoelectric tape reader with thyratron drive which costs about $1,800 and looks quite neat. The other contender is the Ferranti photoelectric tape reader. We are also considering making a simple-minded tape reader of our own which we simply drive the tape without a clutch so that you read simple tapes with extreme speed and don't try to stop between lines. If you have to stop, you must be sure there is a long enough gap between information.

For a typewriter, we have tentatively decided on Sorobon. Another possibility is the Auto Typist made by American Typewriter Company, in Chicago, which is the standard electric typewriter with a very-simple-minded, but rather large, mechanisn.

If we have a separate keyboard, we can use any electric typewriter that has electronic drive, such as the IBM output writer. Soroban makes a saparate keyboard but it's such a simple job we might consider doing it ourselves. One keyboard which we thought about is a set of iron baré, one for each key that closes a magnetic circuit for each of the appropriate codea groups. This mechanism would have the advantage in not having electrical contacts.

We talked to the man from IBM about card readers and card punches but, in general, were quite discouraged because most of their mechanisms have so much more equipment than we really need; but we requested operator manuals and maintenance manuals on each of the possible contenders. The nicest unit is the 026 or 526 key punch which have reading stations and punching stations on them and very nice card handlers, but these machines are very slow and can only read or punch about 15 cards per minute.

CONSOLE FOR PDP-1

We were surprised to find out how much equipment was necessary in the console and so we are redesigning the table. The trend in design of modern tables now is to have the legs extend all the way to the corners. This will make it powerful for us to fit more equipment in. The back side will contain space for eight 19" x 5¼" power supply type panels or system mounting panels and four 3½" panels.

This will allow us to put filtering, contractors, typewriter control panels, and high voltage power supplies and anything else we need back there and still keep the top of the console quite free.

Date December 15, 1959

To Jim Myers/Harlan Anderson

From Ken Olsen

Carl Beckman, who used to work for Burroughs and is now a consultant, has been making studies for IT&Tand Earl Page told him about our computer. He looked over the specifications and thinks it's the hottest thing around and something that IT&T and the Ordanance Department should use. I told him what I could over the phone and he was very enthusiastic and thinks we have a machine much better than the CDC machine. He is going to send a letter and from that we can get his address.

Date December 15, 1959

To Jim Myers/Harlan Anderson

ITT IT&T Interest in PDP-1

From Ken Olsen

Carl Beckman, who used to work for Burroughs and is now a consultant, has been making studies for IT&T and Earl Puge told him about our computer. He looked over the specifications and thinks it's the hottest thing around and something that IT&T and the Ordiunance Department should use. I told him what I could over the phone and he was very enthusiastic and thinks we have a machine much better than the CDC machine. He is going to send a letter and from that we can get his address.

Date December 11, 1959

Bi-Weekly Report

From Ken Olsen

PDP-1 Terminal Equipment

The Flexowriter fell flat on its face during the EJCC, and we cannot tolerate it from now on. For a tape reader, we are considering the Digitronics photoelectric tape reader with thyratron drive which costs about $1,800 and looks quite neat. The other contender is the Ferranti photoelectric tape reader. We are also considering making a simple-minded tape reader of our own which we simply drive the tape without a clutch so that you read simple tapes with extreme speed and don't try to stop between lines. If you have to stop, you must be sure there is a long enough gap between information.

For a typewriter, we have tentatively decided on Sorobon. Another possibility is the Auto Typist made by American Typewriter Company, in Chicago, which is the standard electric typewriter with a very-simple-minded, but rather large, mechanisn.

If we have a separate keyboard, we can use any electric typewriter that has electronic drive, such as the IBM output writer. Soroban makes a saparate keyboard but it's such a simple job we might consider doing it ourselves. One keyboard which we thought about is a set of iron baré, one for each key that closes a magnetic circuit for each of the appropriate codea groups. This mechanism would have the advantage in not having electrical contacts.

We talked to the man from IBM about card readers and card punches but, in general, were quite discouraged because most of their mechanisms have so much more equipment than we really need; but we requested operator manuals and maintenance manuals on each of the possible contenders. The nicest unit is the 026 or 526 key punch which have reading stations and punching stations on them and very nice card handlers, but these machines are very slow and can only read or punch about 15 cards per minute.

CONSOLE FOR PDP-1

We were surprised to find out how much equipment was necessary in the console and so we are redesigning the table. The trend in design of modern tables now is to have the legs extend all the way to the corners. This will make it powerful for us to fit more equipment in. The back side will contain space for eight 19" x 5¼" power supply type panels or system mounting panels and four 3½" panels.

This will allow us to put filtering, contractors, typewriter control panels, and high voltage power supplies and anything else we need back there and still keep the top of the console quite free.