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Evolution of the 1401 Control Panel

There were several designs for the IBM 1401 Control Panel before the design of the machines we have which included the "Overlap" feature, added after original release to fight off competition.
- Background, A-Test, B-Test, C-Test
- A-Test
- B-Test

Background, A-Test, B-Test, C-Test

From IBM 1401 Memories from Endicott by John Pokoski
(paragraphs two and three in "The Race for an Inexpensive Accounting Machine" )

"When I joined the group, much of the design of the first prototype was completed, and it was being assembled in the lab. After testing and debugging in our own lab, it moved on to a separate group called "product test" that had to independently check it for meeting specifications and for reliability. This was called "A-test". Temperature, humidity, and power variations were used in this testing. If it passed ok, and the market was still there, the machine was announced, and the salesmen went to work.

"While this was going on, a second prototype was being built, incorporating everything learned, all engineering changes, some new technology, and optional features. This would be the prototype used for manufacture, and would also go through product test ("B-test"). The first machine manufactured at the factory went through "C-test". Once the machine was announced, training courses had to be set up for salesmen, programmers, customer engineers, factory engineers and technicians, and even customers. This was truly a big operation, and a lot was at stake."

A-Test Control Panel

Jud McCarthy mailed a copy of a photo he used on the cover of his book to Robert Garner.
This picture was labeled "JudMcCarthy_1401SysATestUnit_1959.jpg", implying a prototype pre-production unit.

Robert noticed differences between the IBM 1401 "A Test" Control Panel in the above photo, (left)
     and the production systems on display and demonstrated at CHM. (right)

"A Test" Control Panel - 1959

Production Control Panel - 1963

So he sent the following to Jud -
Besides cosmetic differences, do you recall how the control panel's buttons and switches evolved from System A to the product version? And what motivated them ? I've attached photos of each below (the latter of the CT 1401 panel, w/o Overlap). My observations/questions. :)

  1. There are five error indicator lights on top. I (naturally) assume RAMAC, External I/O, and Overlap were the added ones?

  2. Since the hardware multiply/divide hardware option came later, there are clearly no A and B Auxiliary Register buttons.

  3. It looks like there are four rotary function switches in place of the two "now" on the right side. The other two rotary switches were for...(power on/off)?

  4. The "instruction length" indicator changed shape and moved from below to above the pushbutton switches. (The pushbuttons also moved above the rotary address dials).

  5. The emergency power switch swapped sides. An "endianness" rationale? :)

  6. There are seven pushbuttons on the bottom row compared with only two on the prototype(?), which I assume were Start and Stop?
(A reflection of Fran's optimism(?), as I understand you guys firmly established the need for a Reset button and Check Reset and disabling of I/O Check stop.)

If Start/Stop, your finger is then likely pointing at the Start button?

What about Power On and Off? Previously a rotary switch? What about Tape Load?

And what prompted Tape Backspace to make its way to the front pane?

Do you recall anything else about the control panel design and changes? :)

(Fran proudly recounted to me how he had personally designed the layout - a reflection of the data paths.)

B-Test Control Panel

E-mail from John Pokoski - Oct 23, 2020
Subject: Control Panel Changes from 1401 System A to production version


I can't say much about the System A panel as I didn't really work on it. I do know that Fran was the guru of the System B panel and he was very possessive and controlling of its layout and organization. Personally. in addition to being very informative as to data paths and registers and very pleasing aesthetically, the panel(s) made the system much easier to troubleshoot. The "customer engineering" panel (below) was extremely useful for debugging and I seem to recall a couple of suggestions for additions in B test that Fran approved and were later included. It is interesting that Fran still showed pride in "his" panel fifty years later. I think he was very proud of his artistic abilities (even his signature) and rightfully so. As I have said previously, I consider Fran a true Renaissance man, and pretty much a creative genius.

I don't know if I had mentioned that after the 2009 fest at the museum where Fran and I reconnected at a different level, we communicated fairly often by email. He consoled me about the loss of my wife and encouraged me to get busy with the women again as he had remarried after losing several wives. He really tried to pep me up, and he succeeded. He used to send me various puzzles or magic tricks he had run across on utube and wanted my opinion. Some I figured out, but he had solved all of them. He also asked me about the re-designed multiply-divide system and why it was cheaper. When I explained that it was because the programming group had agreed to allowing the multiplier field to be addressed differently, enabling less scanning of the field, thus less hardware, he was relieved and satisfied. He said, "Oh, sure!" He had designed the original M/D system and probably was concerned that he might have messed up.

I was deeply saddened at his death, but not too surprised. He was not pleased with his condition. I recall that when he began his talk at the museum, I was nervous that he would lose it. But then he really grabbed the audience, and held them in the palm of his hand. I told him this in our emails and I am really glad that I did.

Your planning and organization of the 1401 anniversary party at the museum made Fran happy as well as some others like Chuck and Jim and Earl Bloom who are no longer with us. Plus some other old farts who are still hanging on.