Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!wuarchive!sdd.hp.com!caen!server.cs.uri.edu!reynhout From: reynhout@cs.uri.edu (Andrew Reynhout) Newsgroups: comp.sys.mac.programmer Subject: Re: TicksCount Message-ID: <1991Jun13.111156.25658@cs.uri.edu> Date: 13 Jun 91 11:11:56 GMT References: <5721@hemuli.tik.vtt.fi> <1991Jun11.092513.14329@cs.uri.edu> <1991Jun11.185747.9300@athena.mit.edu> Organization: University of Rhode Island, Computer Science Dept. Lines: 36 In article <1991Jun11.185747.9300@athena.mit.edu> captkidd@athena.mit.edu (Ivan Cavero Belaunde) writes: >In article <1991Jun11.092513.14329@cs.uri.edu> reynhout@cs.uri.edu (Andrew Reynhout) writes: >>In article <5721@hemuli.tik.vtt.fi> aku@tik.vtt.fi (Arto Kujala) writes: >>>Is there a way to get more accurate time than function TickCount >>>gives? >>> >>>1/100 sec precision would be appropriate. >> Unfortunately, you'd need discrete hardware to do this. The Mac gets its >>clock signals from the 60Hz AC input. Of course, it would be very *simple* >>hardware...perhaps there is something out there. > >Actually, the Mac gets its clock signals from crystals (I shudder to think >of a Mac getting its working frequencies from Boston Edison ;-), which >generate interrupts at specified intervals via counters in the VIAs. Yes, several people have taken the time to correct me here. To clarify, I was under the impression that the Mac got its source for TicksCount (not the "clock" as I said previously) from the vertical retrace of the monitor, which I, for some reason, believed to be synchronized with the 60Hz of the AC power line. That's not how it's done, and I apologize for opening my mouth so soon. Apparently, the Time Manager is documented in IM VI. I'm still wading through the first four volumes and coding on a Plus. I guess it's time for me to update myself, eh? :-) [as I flip through IM I to see if there was any truth to my mistaken belief, I find the following: "TickCount (NOT TicksCount!) is incremented during the vertical retrace interrupt, but it's possible for this interrupt to be disabled." (So I was still wrong, but at least I have a reasonable explanation for my error. :-) Thanks for not flaming too hotly.] Andrew --