STE DMA sound system

[exxos]

anyway, that is a great idea, there are a lot of free memory slots per scanline for more sound DMA channels

Is there ? I kinda assumed DMA sound was being sent every scanline ?

[Cyprian]

It more or less looks like this - every 50Hz scanline has 256 memory slots (16bits each). Even slots assigned to the CPU/ACSI/BLiTTER, odd for the SHIFTER, Sound DMA and a memory refresh. From that 128 odd memory slots the SHIFTER eats 80 (or 84 if horizontal scrolling is used), therefore we have 48 for the Refresh and Sound DMA.
That is a theory. I wonder how many cycles per scanline in the STE is eaten by a memory refresh process.

[exxos]

I half recall seeing at some point some demo which used DMA sound playback and there was some corruption in the left border because of the sound. But this was many years ago now. But I only remember it being maybe a couple of lines of corruption the left border or something like that. Which would mean the rest of the vbl would be free for other use. Like I also say, I don't understand the "math" of how it adds up to 50khz playback.