Geoff Blake wrote:
I don't know about 60Hz timebases for older UNIX systems, but I do
remember low end frequency counters being offered with mains derived
timebases - I remember them as a catalog item, I never saw one!
I think they were offered by Systron Donner and this was probably back in
the '60's. They even did a 50Hz option - it must have been a real
time-nuts guessing-stick!
HP did the same thing, and I have one of those. The HP could be trimmed
to 50 Hz, 60 Hz or 100 Hz as the phantastron divider would generate 10
Hz for the 0,1 s gate time. Considering that this is a 5 digit counter
(ehm.. actually there is no digits but columns of 0 to 9 bulbs) it may
work well enought for most applications. For highend users there is a
high-stability crystal option, which is a 100 kc crystal oscillator
divided down by a set of 3 phantastrons to 100 c and then replaces the
mains feed. My counter has the crystal option. :)
As for the original question, I beleive that DEC have provided mains
feed already from the PDP-1. I seem to recall it. For UNIX the PDP-7 and
PDP-11 is the relevant early machines. But getting the 50/60 Hz does not
get you local or GMT time (which was relevant then) so you still had to
set it from armwatch or use a modem service.
Cheers,
Magnus
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