Re: [hatari-devel] Little question about STE DMA sound

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

On 06/01/2012 23:47, Laurent Sallafranque wrote:
> Hi,
>
> I was looking at the changes in the STE DMA sound (FIFO change).
>
> I ask me a question, when the DMA fills the FIFO, doesn't it generate
> WAITSTATES for the 68000 ? (or extra cycles ?)
>
> Regards
>
> Laurent

Hello

I don't think ; the DMA fills its fifo when the shifter doesn't display 
anything (during the right border, end of hbl).

So, the DMA uses the bus cycles that are not used anymore when the 
shifter has nothing to display ; this means it doesn't slow down the CPU 
(it would be different for the FDC DMA access, where cycles are "stolen" 
from the cpu (else, display would stop/have "holes" when accessing 
floppy disk)).

On STE, the only problem could be when removing right border and playing 
stereo sound at 50 kHz, maybe in that case there could be not enough cpu 
for the sound dma (I don't have an STE to really test this).

Nicolas