Darkhog Posted April 15, 2013 Share Posted April 15, 2013 How many cycles does Atari perform in one "frame" (time between changes to RTCLOK)? I'd like to know values for both NTSC and PAL. I need to know it to time my music routines properly. Quote Link to comment Share on other sites More sharing options...
russg Posted April 16, 2013 Share Posted April 16, 2013 How many cycles does Atari perform in one "frame" (time between changes to RTCLOK)? I'd like to know values for both NTSC and PAL. I need to know it to time my music routines properly. 1/60 second for NTSC. Probably 1/50 second for PAL. It is called a 'jiffy' and 8000 'machine cycles' can be performed in a jiffy. This is from 'Mapping the Atari' location 18,19,20 ($12,$13,$14) Quote Link to comment Share on other sites More sharing options...
cRc_atari Posted April 16, 2013 Share Posted April 16, 2013 PAL - 35568 cycles NTSC - 29868 cycles Quote Link to comment Share on other sites More sharing options...
José Pereira Posted April 16, 2013 Share Posted April 16, 2013 PAL - 35568 cycles NTSC - 29868 cycles Yes. The two has always same 114cycles per scanline happening each frame 50 or 60 times each second. Then it's up to each T.V. Type: NTSC: 114cycles x 262scanlines PAL: 114cycles x 312scanlines To this available you have to discount your coding instructions and the screen GR. Mode and if 32, 40 or 48Bytes wide but also the number of scanlines you have with something shown on screen (for example: if just playing music and all screen scanlines are Blank/not used then the screen display takes no cycles. That's why why greatest A8 pieces of music just play on an empty/black screen). Am I right? Quote Link to comment Share on other sites More sharing options...
Rybags Posted April 16, 2013 Share Posted April 16, 2013 Blank screen music quality relates to digital sample playback - it can be done in active screen but timing is better on blank. Generally for chiptune stuff you just use the VBlank NMI which will always be ~ 50/60 Hz. A cheap way to maintain constant tempo is to develop the music as if destined for Pal. Then if NTSC is detected, skip the play routine every 6th frame. Timing will be slightly out but hardly detectable and tempo will be near exact on both systems. Quote Link to comment Share on other sites More sharing options...
Darkhog Posted April 16, 2013 Author Share Posted April 16, 2013 (edited) Well, I plan to make game, so blank screen is out of a question . Anyway, thanks everyone for help. You're great. Sorry for being nuisance. Edited April 16, 2013 by Darkhog Quote Link to comment Share on other sites More sharing options...
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