The garage of a ranch house in Texas on a hot afternoon, under the ceiling a garage door opener with its beige sheet-steel cover hanging open, inside it a small circuit board of brown pressboard turned toward the lens, on it a black plastic chip three and a half centimetres long with twenty-eight short silver-grey legs and two shallow round dimples at its ends, plain smooth and unmarked, a small relay in clear plastic, a coil of copper wire, a man in a short-sleeved plaid shirt on a step ladder seen from directly behind with his face turned fully away, reaching up with a screwdriver, a pale green station wagon below.
What it was used for
A 4-bit microcontroller family from Texas Instruments, announced in 1974 and, per the Computer History Museum, priced at 2 USD in volume. The same page names burglar alarms, garage door openers, games and toys, among them "Speak and Spell", as applications. Its foundation was the single-chip calculator part TMS1802 designed in 1971 by Gary Boone and Michael Cochran. Boone describes that earlier project in his IEEE oral history: work began about December 1970, parts worked on 4 July 1971, and the chip paid back its development costs eighteen times over in the 4 months left in 1971.
What was new
What marked it was the consolidation: program store (ROM), data store (RAM), a BCD arithmetic unit and keyboard and display scanning on one die - Boone describes this as pulling together what normally took 3 or 4 chips. Unlike the calculator-bound TMS1802 of 1971, TI offered the 1000 series, per the Computer History Museum, as a general-purpose 4-bit family. Boone says the controller idea - taxi meters, digital voltmeters, counters - was there from the start, and that on the earlier project the team built no breadboard and used simulation instead; he believes that was the first major microprocessor project to skip one.
What the sources leave open: Boone's oral history calls the earlier project "TMS-100", not TMS1802; the figures are assigned to the 1971 chip by context and by the Computer History Museum. Data-sheet values (ROM, RAM, pins, clock) are missing here. Per the Computer History Museum, Boone's patent 3,757,306 was filed on 31 August 1971.
Connections
Every connection names its kind. “Forerunner” on its own would be a claim.