I'd say it looks as much like firmware as a PROM
implemented as a
of diodes, some of which have been cut. :-)
So, Wang Laboratories made a series of machines it called the
100-series. There were display (Nixie tube) and printing versions of
The logic of the machine was small-scale DTL/TTL IC's.
It was a microcoded architecture.
The microcode sequencer consisted of a TI TMS 2600 ROM, which took
inputs from various state flip flops, and generated control signals that
ran the microcode through the sequences. The microcode itself
was...wait for it...
Two large circuit boards populated with diodes! The microcode itself
was "hard wired' in diodes.
The machine was developed at a time that MOS ROM wasn't quite there in
terms of size and cost to hold the microcode, so the diode ROM was used.
Question is: Is the diode ROM "firmware"?