>> Who built a computer that cared about AC frequency to drive the real >> time clock? Never heard of anyone doing that. > > My first computer, a Poly-88 8080 based system, did (I still have it). > <http://www.polymorphic-computers.com/poly88.html> > > The transformer used for the linear power supply was tapped, rectified > and clamped to feed to an interrupt pin. The interrupt routine would > increment a counter in RAM which was accessible for real time > calculations. > The Commodore PET and 64 had a 60Hz real-time-interrupt that did a bunch of housekeeping. You could patch your own routines into it, which was really handy.
After a particularly nasty bug, that's where I learned about the importance of semaphores in controlling access to shared resources ;) -- Peter Hiscocks Syscomp Electronic Design Limited, Toronto http://www.syscompdesign.com USB Oscilloscope and Waveform Generator 647-839-0325 --- Talk Mailing List talk@gtalug.org https://gtalug.org/mailman/listinfo/talk
