During the reverse engineering scene I would assume that they are reading the BIOS which would have been stored in ROM (Read Only Memory). The ROM chip would ha

During the reverse engineering scene I would assume that they are reading the BIOS which would have been stored in ROM (Read Only Memory). The ROM chip would have the same address and read control lines like any standard memory chip which could be read by setting the Address lines, the Memory Read, any additional/ancillary signaling and then reading the data lines. Once you had all the bytes read, you could in principle run this through a Disassembler to get the actual Assembly language instructions (minus any original comments). You would have to figure out the boundaries of code, data etc. I would assume in those early days, they wouldn't expect the run of the mill hackers to be able to disassemble the stored data in ROM.