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25 votes

Did anybody use PCBs as macro-scale mask-ROMS?

The HP9100A had a ROM which used inductive coupling between adjacent layers on a 16-layer PCB to store data: http://www.hp9825.com/html/the_hp_9100_rom.html. This approach apparently reached a density ...
malte0811's user avatar
  • 351
20 votes

Did anybody use PCBs as macro-scale mask-ROMS?

IBM used punched mylar circuits as ROMs. 0's and 1's were encoded by cutting some traces, circuits were probed through small inductors. http://www.righto.com/2019/11/tros-how-ibm-mainframes-stored....
Grabul's user avatar
  • 3,647
18 votes

Did anybody use PCBs as macro-scale mask-ROMS?

DEC had a bootstrap ROM module for PDP-11's with 32-words of memory: BM792 Unibus Module. Each bit position had a diode. If the diode was snipped out it flipped that bit from 1 to 0. Experienced users ...
HABO's user avatar
  • 721
8 votes

Did anybody use PCBs as macro-scale mask-ROMS?

While I am sure it has been done, keep in mind that concurrent with the beginning of the microprocessor era was also the beginning of the EPROM era. According to the linked Wikipedia article, the ...
manassehkatz-Moving 2 Codidact's user avatar
5 votes

Reverse engineering an old 40-pin connector

With the continuity checker, a pencil, and graph paper, you can usually reverse-engineer a single-layer circuit board like this without even powering it on. First you reverse-engineer the PCB into a ...
Jacob Krall's user avatar
  • 2,289

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