Re: [hatari-devel] Questions on Falcon DMA sound

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 02/04/2024 à 20:25, Eero Tamminen a écrit :
> Hi Nicolas,
>
> Was this checked after 2.3 release?
>
> If not, would you have time to look into it after 2.5 release?

Hi

I don't remember looking at this, I will add it to my todo list for 
after 2.5

Nicolas

> On 27.10.2020 11.17, Nicolas Pomarède wrote:
> > Le 26/10/2020 à 23:08, Roger Burrows a écrit :
> > > On 26 Oct 2020 at 19:39, Christian Zietz wrote:
> > >
> > > > Roger Burrows schrieb:
> > > >
> > > > > Quite possibly the documentation is just wrong.  However, in TOS4, 
> > > > > there
> > > > are
> > > > > manipulations of 'mystery bits' that are not documented in the 
> > > > > development
> > > > > notes or the Compendium.  Specifically:
> > > > >     . bit 3 of $ff8937 is toggled
> > > > >     . bit 2 of $ff8938 is toggled
> > > > >     . bit 3 of $ff8938 is cleared (only)
> > > > > [...]
> > > > > But meanwhile I would be interested to hear comments from the smart
> > > > hardware
> > > > > people about those mystery bits.
> > > >
> > > > There is this collection of technical documents that among other things
> > > > covers the Falcon. Unfortunately, just the document that would contain
> > > > these registers is damaged, so that only the text version (without
> > > > formatting) survives, which is a bit hard to interpret.
> > > >
> > > > There, I can see:
> > > ...
> > > > Hence bit 3 of $FF8937 should be "Global Sound Reset". And...
> > > Thanks!  That's a big help and expands on what I found by a test 
> > > program (which
> > > I have attached).  In the ZIP, Hatari developers please find the C 
> > > source,
> > > Lattice C .PRJ file, and binary for DMASOUND.TTP.
> > >
> > > Also there is FALCONHW.TXT which shows the results of running the 
> > > program on
> > > real Falcon hardware, and HATARI.TXT which shows the output from the 
> > > same
> > > program run on Hatari 2.2.1.  As you can see, toggling bit3 of 
> > > $ff8937 on real
> > > hardware resets a lot of dmasound registers.
> > >
> > > I haven't tried running DMASOUND.TTP with the latest Hatari source in 
> > > the repo,
> > > but since the routines that handle that area of the hardware 
> > > emulation do not
> > > pay attention to that bit, I would be extremely surprised if the 
> > > results were
> > > different.
> > >
> > > I think that now would be a great time to fix this in Hatari, before the
> > > upcoming 2.3, although I realise that there may be some concern about 
> > > changing
> > > the code at a late stage.  In any case, I will fix this on the EmuTOS 
> > > side
> > > shortly and see how that helps on real Falcon hardware.  There may be 
> > > other
> > > things I need to do, but this definitely needs doing.
> >
> > Hi
> >
> > thanks for your tests / programs, they can be used to improve hatari. 
> > But as you say, release is near, I don't think that's a good idea to 
> > change things at this point, it might cause regression, especially now 
> > that laurent/eero went through a huge list of demos/games to update 
> > their compatibility with next hatari 2.3 ; it would mean to recheck 
> > eveything.
> >
> > Nicolas
> >
> > > ...
> > > > Thus, bit 3 of $FF8938 would be "Expand" (whatever that is) and bit 2
> > > > would be "mute". No idea why one would toggle "mute", though. Also, I
> > > > don't know if everything is actually implemented in hardware or some
> > > > bits were only planned for future revisions of the Falcon that never
> > > > came to be.
> > > I will see if I can determine what toggling bit 2 does and what 
> > > setting bit 3
> > > to 1 might do, but that's likely to be difficult.  The toggling of 
> > > bit 2 is
> > > done in conjunction with setting and resetting values in the attenuation
> > > register, so it might be possible to figure it out logically.  If 
> > > anyone would
> > > like to see the relevant TOS4 disassembly, I can post it here (it's very
> > > short).
> > >
> > > Thanks again,
> > > Roger