On Jan 9, 2014, at 4:03 AM, Hal Murray wrote: > > The IBM 360 systems starting in 1964 used the power line frequency. (A > location in low memory got bumped at 300 counts per second. 5 per cycle on > 60 Hz and 6 per cycle on 50 Hz.) I wonder how much the power timekeeping > wandered back then relative to today. > > Does anybody know what the guys in the power company control rooms do about > leap seconds? > > ------------ > > Leap seconds started in 1972. > > I was at Xerox in the late 1970s. At boot time, Altos got the time from a > local time server. Altos used the system crystal (5.88 MHz) for timekeeping. > Personal Altos were rebooted frequently so it didn't matter if their clock > drifted a bit. The time server was packaged with the routers. (We called > them gateways.) On the few systems that were up a long time (file servers, > routers), we hand tweaked a fudge factor to adjust the clock rate. It wasn't > hard to get to a second per week. I think the units for the fudge factor > (from a config file) were seconds per day, but it would read at least one > digit past the decimal point. I don't remember any mention of leap seconds. > > > When were there enough (Unix?) boxes on the net running NTP and keeping good > enough time to notice things like leap seconds? > > I should go browse the old RFCs and see when the API for telling the kernel > about pending leap seconds was published. But somebody may have good stories > or folklore.
I know there were documented problems in the leap seconds that happened in the late 1990s. I was involved in GPS steered OCO in the early 2000's, and they were definitely a problem by then. That's when i developed most of my opinions about their impact on general time keeping and imperfect fit with POSIX and the leap second standard. A fit that's only grown more chafing to this day. Warner _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
