Posting elsewhere about the effect of voltage supply variation, this caught my eye:
Quote:
A customer engineer spent
eight hours a day on the premises, includ-
ing an hour long daily preventive mainte-
nance session before the normal first shift
began. The session included bringing up
power, which took 15 minutes, and running
diagnostics with voltages 20 percent above
and below normal in an effort to find weak
vacuum tubes. The effort was usually
successful.
See
https://archive.org/stream/byte-magazin ... 1/mode/2up(Also noteworthy: three-way branching, and negative indexing.)
In the same issue of BYTE there's an article on the design choices going into the 6809 ("A microprocessor for the revolution"):
https://archive.org/stream/byte-magazin ... 5/mode/2up
