Oh my, "the dark ages" (grin). Much easier for me getting started in '79 and the early 80's. I've still got a little ultraviolet "eraser" on the shelf here which I used on 2716, 2732, and 2764 EEPROM's...
When I authored the earliest version of the current "TV Guide Channel" software, called the United Video "Electronic Program Guide" back then, the program was burned into 2716 EEPROM's and installed as "firmware" in the 19" rack panel Character Generator hardware. I think we did 3 version upgrades during the first year and this simply involved sending out a set of new EEPROM's to the Cable company clients. Their staff would go the the "head end", open up the Character Generator box, pull the old EEPROM's and install the new ones. This wasn't a "big deal" because it took us nearly a year to reach the 1,000,000 subscriber level.
Mike