20 Dec
2005
20 Dec
'05
12:15 a.m.
I think for example in the TRS 80 /I a 7400 with a
defective unused
gate was used because it was cheaper than a working 7400.
I don't recall that, and I've worked on most TRS-80s, and read the
schematics. Of course there are unused gates that could be defecive.
BUT...
I remember a UK company called Bi-Pak. They bought up defective ICs,
tested them [1], and sold them. They did sell things like TTL quad-gate
packages with only 3 good gates. Problem was, as we all found, those 3
gates quickly failed in use.
[1] The tester was built from telephone relays and selectors. It ran at
about 1Hz. Plenty of chips passed that test and failed at more reasonable
speeds.... Don't ask how I found that out.
-tony