I'm kind of proud of this hack. My boss, George Grisinger, a Z-80 fanatic,
really wanted me to make a custom controller board with a Z-80 to do this.
But I am far too impatient to be wire-wrapping hardware prototypes. It was
easier to hack into the existing ROM and write software for the TMS9900-based
computer that was already monitoring the machine. This is a utility to
calculate the speed of the machine in letters-per-minute.
Obviously I would have preferred my calculations for cost savings over those
of my supervisor. But getting more than two or three hundred dollars out of
an award was like getting blood from a turnip.