Examining the core memory module inside a vintage IBM 1401 mainframe
righto.com
righto.com
Seeburg's line of jukeboxes from 1955 onward used this mysterious system called TORMAT, which essentially was a 160-bit toroid memory device (for a jukebox that held 160 selections). Bits were flipped on as you paid for choices and the loading arm seeked the next record by checking the bits in memory. This also had the positive side-effect of people selecting the same record not resulting in multiple plays, since you were flipping on a bit that was already flipped.
https://www.flippers.com/Seeburg-tormat.html
The TORMAT was used up until 1974, when it was replaced with silicon-based memory.
I once had to replace the core memory array when one bit went bad. By pure bad luck, it was in one of the first few columns where the end-of-message sequence was expected, and the bad ferrite meant the system got hung up waiting for an EOM that was never detected. Bad donut. No message. ;/
¹ https://c1.staticflickr.com/1/40/109018526_8edb26b499_b.jpg
The cards for the program to be executed have program code on the left half and loader code on the right half. That is, each card has code to move its program code into the right place in memory, add necessary word marks, and then load the next card. This code is running from the reader buffer (locations 1 through 80). The final card jumps to the location in memory to start execution.
TL;DR: Since the IBM 1401 doesn't have an operating system, when loading a program from cards, each card also contains the code to load itself into memory.
And yes, 4K of memory is 4000 characters, not 4096, because it's a decimal machine, not a binary machine.
Also, what kind of data can you process with 4K? They say "accounting software" and "paysheets", was it actually quicker than writing paysheets manually?
Cards were quite handy, because they were reusable. You could construct a program just using old ones. In university I remember a special box for "100 CONTINUE"-cards.
One interesting thing they did was to thread extra cores onto each wire so they could crush the bad cores and still have enough to continue. (They would test after wiring one direction, before wiring the second direction.)
It would be neat to do though. wonder if you could make one work like an i2c eeprom chip, have it act as a drop-in replacement. Or rather, an "add jumper wires and put in a box outside of it replacement."
Listen to part 1 here: https://www.youtube.com/watch?v=tBw_wSoVQrY
The mainframe of the era was something in the 7000 or 700 series, I think.