In 1977, Intel released the little-known 8271 floppy disc controller (FDC) chip, which was mainly used in business computers and storage solutions. However, it gained recognition by being included in the BBC Micro, a UK-based computer released in 1981. Despite the scarcity of information available about the chip, a team of researchers embarked on a project to reverse engineer its workings. Through their efforts, they discovered that the 8271 was a dual processor microprogrammable chip with approximately 22,000 transistors, making it larger and more expensive than the iconic 6502 CPU. They also unraveled the chip’s Instruction Set Architecture (ISA) and decoded specific commands like “READ SPECIAL REGISTER” and “SPECIFY.” This research shed light on the chip’s inner workings, challenging conventional assumptions about its capabilities.
https://scarybeastsecurity.blogspot.com/2020/11/reverse-engineering-forgotten-1970s.html