Weekly Classic Computer Trivia Question (20150112)

Doug Ingraham dpi at dustyoldcomputers.com
Mon Jan 12 10:10:40 CST 2015

This weeks question comes from Warren Stearns.  It is a little obscure and
specific to the PDP-8 family of computers.

What is the source of the greatest latency in the interrupt system on a

I have three answers, two of the answers depends on the options fitted to
an 8.

Why would this have been an important question?  Interrupt latency would be
extremely important in the field of data collection which was one of the
principal early uses of these machines.  My particular 8 was used for
exactly this purpose in the Summer when it was hauled to a radar site and
collected weather research data for the Institute of Atmospheric Sciences.
I believe it was used for this from 1969 through 1972.  I have several
hundred DECTapes with some of this data.  The surprising thing is we don't
see any problems reading DECTapes that haven't been out of their box since
the early 70's.

Doug Ingraham
PDP-8 S/N 1175

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