19 Dec
2010
19 Dec
'10
7:26 p.m.
On 2010 Dec 19, at 10:28 AM, William Donzelli wrote:
And as for DEC - remember that they sometimes used ICs
in somewhat
unorthodox ways that may not be tested for back at the vendor. It seem
to recall that one of their favorite tricks was to use some of the
internal "diodeness" of the input and output pins of line transmitters
and receivers for clamping.
I'm reminded of the PDP-8/m front panel problem discussed on the list a
few years ago, where the design was relying on non-specified behaviour
of an IC type and turned out to be very dependant on both the
manufacturer and time frame of IC production.
(Collector triggerring of a 74175 FF:
http://classiccmp.org/pipermail/cctalk/2006-September/224592.html)