Re: [hatari-devel] Fix for Falcon's noisy sound

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 06/10/2016 à 00:12, Nicolas Pomarède a écrit :

> There's a second problem with falcon sound : sometimes, there's no DMA
> sound at all (I often get this with 030 demo by Doug). This is a
> different issue, but the good news is that I found a way to fix it too.
> I need to fully check it, but I'm confident this will be OK.

Hi

regarding this problem, a case to reproduce it would be the following :
I want to watch "030" demo by DML, so I start Hatari in Falcon mode.
As this demo requires FPU + more RAM, I press F12 and set FPU to 68882.
When I exit pref screen, Hatari asks to reset the machine to take the 
changes into account.

At this point, this is where the crossbar 25 MHz interrupt gets 
completely disabled and never gets active later. So there's no more 
sound under Falcon in that case ;(
But if you start Hatari with FPU already enabled and don't need to reset 
it to change prefs, then sound will be OK.

This is why some people (including me :) ) often had the feeling of 
sound randomly not working at all.

There's a nasty situation at the moment where shortcut keys are tested 
during the internal VBL handler. But if the shortcut requires a reset, 
then the VBL handler will still try to ack the current int, except it's 
not the VBL anymore, it can be any int that was re-enabled during the 
reset part.

In the case of the falcon, this nuked the 25 Mhz sound int used for DMA 
sound :(

This is now fixed, so hopefully Falcon DMA sound should be really more 
stable now. A better fix will be made after Hatari 2.0 is released, to 
handle shortcut keys in the main cpu loop, not during the interrupt' 
callback handler.

Let me know about game/demo/program not using DSP for sound that would 
still not work, I hope there's not that much now :)

Nicolas