Hi My second home computer was a PDP=11/20. The first was a PDP-8E. Both are long gone...
Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Uno Staver Sent: Tuesday, April 20, 2010 8:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 60Hz mains clocking in computers Since many of us are not so old as I am, and aren't familiar with the PDP-11 family, I should have mentioned that this happened in the middle 80's. Uno Staver wrote: > We bought a bunch of PDP-11/23s as part of a communications network > system. After successful acceptance tests in Boston, MA, the systems > were commissioned in Sweden with 50Hz AC. To make the RSX-11M O/S > time-of-day clock run OK, the developers modified some piece of code. > > > Uno Staver > > > Bill Hawkins wrote: >> Yes, the whole PDP-11 line used line frequency to update the real-time >> clock. >> DEC had a real-time operating system, very useful for emulation of analog >> process control functions. Of course, an RTOS is more than just the >> clock. >> >> We lost that anchor to real time in the interval between the PDP-11 and >> NTP or SNTP when the microprocessors took over. All crystal clocks; time >> of day (social time) set by anybody with a wristwatch. >> >> Bill Hawkins >> >> >> -----Original Message----- >> From: paul swed >> Sent: Saturday, December 12, 2009 10:09 PM >> >> Talk about dusting off the old brain cells. >> I seem to remember that the PDP 11/23s did indeed allow the use of the >> 60 hz >> as an interrupt for precision timing if that can actually be said. The >> data >> general nova 1200 also. Boy thats exposing ones age. >> >> On Sat, Dec 12, 2009 at 8:29 PM, Colby Gutierrez-Kraybill < >> co...@astro.berkeley.edu> wrote: >> >>> I'm trying to get to the bottom of whether or not any computing >>> equipment >>> made around the advent of UNIX systems (or any time-slicing system) used >> the >>> mains cycles of 60Hz as phase lock for the internal system clock. My >> guess >>> is that perhaps they did not as the computing logic is DC based, but, I >> have >>> memories of using an 68000 based UNIX system that I thought had its >> internal >>> clock based off of the 60Hz mains... Not sure the vendor anymore. >>> >>> Thanks, Colby >>> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
