2 Jun
2006
2 Jun
'06
5:12 p.m.
Early 7400-series TTL had the 7450 and 7453
AND-OR-INVERT gates that could
be explanded with another 4 inputs via the 7460 dual 4-input expander. I'd
hate to own equipment now that used some of those that required
replacement--they must be very difficult to find.
There were at least 2 different expanders, I forget the number of the
other one.
The HP98x0 machines use these gates as the input selectors to the
bit-serial ALU (and I think to the T register (memory data register)). I
did have a 74H52 fail in one 9810 (that's an AND-OR gate), fortunately,
not much of it is used in _that machine_ and I could dead-bug in a
74LS51. That wouldn't work in the 9830, or I assume the 9820 (not looked
at the hardware of that machine yet, next project) as those use rather
more input sections of the AND-OR gate.
-tony