I know there were folks (Ed?) who discovered, within the last couple of years, that the old Intel 8271 and 8273 controllers were the same part and were actually (and somewhat covertly) a microprocessor. The 8271 was a floppy disk controller and the 8273 was an HDLC/SDLC link controller.
I worked on a project that used this device. The part was very buggy and forced a lot of overhead on the little 8-bit processor (8085). Overall a good learning experience but a bad project experience.
This morning, I happened to recall one of the specific issues: supposedly our hardware folks eventually got an errata sheet from Intel, and one of the chip’s pins was an undocumented open drain requiring an external pullup resistor. Today I reviewed the data sheet, and although it’s an image (not searchable), I didn’t see indication of any open-drain outputs. I might have just missed them.
So my question is: did the team that recently reverse engineered this device discover that any of the output pins were open-drain rather than the usual (for the day) superbuffers, or is my information wrong? It would be a kick to re-discover the open drain pin, after all these years.