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Wow what a fascinating post this was. I had a questions and a comment. >The IBM 1401 could also boot from a magnetic tape using a similar process; pressing th

Wow what a fascinating post this was. I had a questions and a comment. >The IBM 1401 could also boot from a magnetic tape using a similar process; pressing the "Tape Load" button on the console loaded a record from tape, just like booting from a card. Were the tape consoles prohibitively more expensive at the time? Were there certain workloads that lent themselves to magnetic tape vs punch cards or was this purely an economical concern? >"The photo below shows the card that implements this flip-flop. With the 1401, you can actually see the physical transistors that implement each function." Would you consider diagraming out that card like you usually do for circuits? I think that would be great addition or maybe even a separate blog post(s) on discrete CPU components in these old mainframes? Lastly where did you manage to find access to a working IBM 1401?

kens 6y ago
Tape drives rented for about $1000 a month ($9000 in current dollars). Tape drives were pretty common because they could hold much more data than cards. However, everyone used cards for data input because you couldn't enter data directly onto cards. Sorting was tricky on tape drives; you typically needed 4 drives. Cards were also more reliable since it's pretty hard to destroy a card unless you burn it. (Even if someone rips up a card, you just look at it and punch a new one.) IBM's documentation explains how the cards work in detail. I've put the information for each card online. For instance, the CW card in the article is described here: http://righto.com/sms/CW http://righto.com/sms/CW (Click the arrows on the schematic to get to the text description.) I used the IBM 1401 at the Computer History Museum in Mountain View, California. They have two working 1401s.
- bogomipz 6y ago
  Ah neat. I somehow missed the clickable schematic cards. Good stuff. Cheers.

kens 6y ago

Tape drives rented for about $1000 a month ($9000 in current dollars). Tape drives were pretty common because they could hold much more data than cards. However, everyone used cards for data input because you couldn't enter data directly onto cards. Sorting was tricky on tape drives; you typically needed 4 drives. Cards were also more reliable since it's pretty hard to destroy a card unless you burn it. (Even if someone rips up a card, you just look at it and punch a new one.) IBM's documentation explains how the cards work in detail. I've put the information for each card online. For instance, the CW card in the article is described here: http://righto.com/sms/CW http://righto.com/sms/CW (Click the arrows on the schematic to get to the text description.) I used the IBM 1401 at the Computer History Museum in Mountain View, California. They have two working 1401s.

bogomipz 6y ago
Ah neat. I somehow missed the clickable schematic cards. Good stuff. Cheers.