The Making of the MCM/70 - Inventing the PC - page 42

This rack of hardware is the first
working prototype of the MCM /70,
constructed in 1972. The “rack com-
puter” contained three cassette tape
drives on the top, a row of wire-
wrapped cards below the drives,
and a blue panel with a SelfScan
display and switches mounted in the
middle of the rack. On the bottom
of the rack, there was another row
of cards and the computer's power
supply. (Photograph courtesy of
Cam Farnell.)
Self-Scan 32-character display). 4 Soon afterward, the software
group started to port a subset of APL into the prototype's
EPROM s. Laraya vividly remembered some of the first compu-
tations done on the prototype.
The first time we did a calculation [on the prototype] …
it took forever to crunch out the number. You could see
it [a long computation] happening on the workspace too,
because, at one point, we were using the display area [al-
located in RAM ] as a temporary workspace … because we
were so tight on RAM . You could see the numbers rolling
up and down on the screen. And you could see, oh, that's
about finished, because you could read the bits … you
could see that there was a counter decrementing and when
you saw that the counter dropped to zero, it would flash
the answer. So, it was fascinating to look at that small
screen.