[email protected] said: > 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.
The IBM 360s bumped a memory location each cycle of the power line. They bumped it by 6 in 50 HZ countries and by 5 in 60 HZ countries. So the units were 300ths of a second. I think that was used for the system time-of-day clock. (I assume it was a few lines of microcode.) > 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. I'm not sure what "DC based" means. For something like this, you would need an IO device that generated an interrupt. It's a pretty simple IO device, but as far as the CPU is concerned, the power line is part of the outside world. Most of the hardware for this sort of IO device would probably be filtering out noise. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
