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Media Formats, No Numbers and Netcat

Andrew Back
Open source (hardware and software!) advocate, Treasurer and Director of the Free and Open Source Silicon Foundation, organiser of Wuthering Bytes technology festival and founder of the Open Source Hardware User Group.


April 24, 2014 16:35

Another lesser-known read only memory media (besides hand-wired diode matrices) actually used punch cards for microcode storage on some IBM computers.

The cards could be punched on a standard keypunch, and could be changed out in the field to load different microcode for emulating other computer models.

Readout used capacitive sensing. The cards were installed between sense electrode boards and an inflatable metalized bladder (air bag) that kept the cards pressed against the sense electrodes boards. These were sandwiched, with cards on either side of the air bag, and the sense electrode boards on the outside. You can see the patent with more info at .

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