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How much CPU does POKEY music/sfx use up?


Xebec
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I'm pretty sure a generic answer could be 1-100% (digital sfx), but i was just curious - for a typical game with 3-4 channels of music, and maybe 1 channel of sound effects - how much of the available CPU time is given up for POKEY? (and how much bandwidth does POKEY end up needing for sound output?)

 

Does using a pokey channel in 16-bit mode substantially change the cpu usage?

 

 

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Pokey doesn't take CPU to make sound. CPU is only involved when changing what it's doing. So.. if you are changing the sounds a lot, it will use more CPU. Playing digitized 4-bit sound would be the prime example. Setting each channel to play a tone/sound will continue to play those tones with no further CPU involvement. Complex music with lots of effects will use more CPU.

Edited by Nezgar
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It can be highly variable depending on tracker or playback software used. Some music pieces like RMT executables give a clue with the ongoing background colour change from grey (busy) to black (idle).

 

A simple bit of music done by custom program with no ADSR or frequency sweep processing might only take a couple of scanlines.

Generally a RMT piece with typical envelopes and freq sweeps on 3-4 voices takes about 20-40.

A stereo piece can take twice that.

 

NTSC has 262 scanlines available and in the onscreen area you get less done thanks to Antic DMA steals so realistically a quad Pokey setup would likely occasionally run into trouble.

A strategy if CPU gets tight at times could be to buffer ahead then skip music processing in frames where CPU is lacking.

 

16 bit sound, there's less support from existing trackers but it would take more than 1 voice on 8-bit sound. But then you get some back in that you're not doing note processing for the other channel involved.

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It also is depending on how the sound is programmed. How many channels, pitch changes, volume... and so on. In RMT you have some control over it by using small envelope tables, instead of using the automatic vibrato volume change or pitch tune.

For a stock Atari and a well done tune, you can do an approximation at 5% CPU usage.

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my experiences with using different music/trackers in various releases...

 

RMT is the most time consuming tracker, if you need as much as CPU power for program and need to use RMT I tend to say to my music guys... only 4 channels please (not 8 channels/stereo) and do not use SID-Voice in RMT...

 

Or in other releases where RMT is not the best, I let e.g. Miker compose in Music Pro Tracker as its more "tight" tracker in CPU & RAM footprint. e.g. in Arsantica 3 Wolfenstein part we had only few hundred of bytes for music and player where it was a no go for RMT with its memory hungry "buffers" imho.

 

if you want to have e.h. digi drums track in parallel again MPT is the way to go where it depends if 8 Khz samples or 15Khz samples are played back... of course 8 are less time consuming than 15. but here you have not much CPU left not to interrupt the digi playback.

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my experiences with using different music/trackers in various releases...

 

RMT is the most time consuming tracker, if you need as much as CPU power for program and need to use RMT I tend to say to my music guys... only 4 channels please (not 8 channels/stereo) and do not use SID-Voice in RMT...

Why no "SID" voice? this doesn't really eat much ... or much more than standard 4 channel programming...

 

This "SID tune" , which is basically really a SID tune played by POKEY, eats up 5-10% ...

 

 

 

 

 

some added "tables" for some nicer music isn't also the end of all development ;)

Edited by emkay
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