This pretty chip from 1981 helped connect an IBM mainframe to data-entry terminals. 1/14
@kenshirriff One question that may sound really stupid but "I really cannot understand", you reverse engineer those IBM chips ... But .. does it mean IBM has lost all the lore about them or they don't want to make it publicly available ? Why ? And if that's the case "why they don't come after you for exposing it ?". I mean it's all super cool, super clever, "tremendous exercise" but does it mean "original documentation is lost forever" ??
@gilesgoat That's an interesting question. Companies never expose the full details of their chips. The one exception that I know of is that someone talked Intel into releasing the masks for the 4004 processor: https://4004.com/mcs4-masks-schematics-sim.html
@kenshirriff @gilesgoat There is a story of a Russian chip that obviously reverse engineered a TI chip since the TI logo is on the chip. There is also a story of a RE chip (PDP-11 I think?) with a Russian something to the effect "steal from the best"
Later chips and the piracy race made it much harder ...