Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!uwm.edu!linac!att!pacbell.com!tandem!zorch!sega0!mykes From: mykes@sega0.SF-Bay.ORG (Mike Schwartz) Newsgroups: comp.sys.amiga.programmer Subject: Re: Is OS supposed to zero the TOD clock registers intermittently? Message-ID: Date: 24 Mar 91 06:19:43 GMT References: <1991Mar21.175806.23729@daffy.cs.wisc.edu> <1991Mar22.011550.23658@watdragon.waterloo.edu> Organization: Amiga makes it possible Lines: 29 In article <1991Mar22.011550.23658@watdragon.waterloo.edu> ccplumb@rose.uwaterloo.ca (Colin Plumb) writes: >pochron@cat17.cs.wisc.edu (David Pochron) wrote: >>In my (apparent) never-ending quest to figure out why my clock keeps going >>haywire when I drag windows around, I decided to look at the 8520 registers >>$BFD800, $BFD900, and $BFDA00 (CIAA-eventLSB, eventMid, and eventMSB for >>those who remember mnemonics) and see what happens to them when this "blessed" >>event occurs. > >Well, my 1.3 Hardware manual says that CIA A is BFEx01 and CIA B is >BFDx00, so you're looking at the CIA B TOD register, which is used >by the graphics.library to synchronise events to the video beam, >i.e. QBSBlit(). > >I can see why heavy graphics activity could use this counter heavily. > I wonder why they don't just use Copper interrupts at the desired scan line? This would be exactly in sync with the beam and would free up the CIA timers for programs to use. >-- > -Colin -- mykes ******************************************************* * Assembler Language separates the men from the boys. * *******************************************************