Re: [hatari-devel] DSP for Previous

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On tiistai 02 kesäkuu 2015, Laurent Sallafranque wrote:
> I did a lot of integeration of the DSP part into Hatari.
> 
> Actually, the DSP is quite completly integrated for the Falcon (there
> are a few known things that should be done, but it works quite well).
> There's no DMA to DSP into the Falcon, so this is not emulated.
> If the computer has 2 or 3 external RAM banks, this may need to be
> reworked too, so may be the memory mapping.
> 
> The instructions pipeline is not perfect with some instructions that use
> Rn registers, but it works anyway in an emulator.
> This makes some problems when someone use the emulator to develop
> something for the real hardware.
> 
> Don't hesitate to ask for more informations if needed.
> 
> As an example, Doug Little has ported Doom and is currently porting
> Quake 2 on Falcon by only developping on hatari.
> He tests his code on his real falcon sometimes, but this shows that the
> emulation level of the DSP is quite high.

I think this needs some clarification.  Douglas doesn't use DSP
for sound processing which is the normal usage for them, but
for graphics processing. :-)

I would also call those things more than just ports.  They're basically
rewrites of the Doom & Quake rendering engines in mix of DSP and m68k.
In BadMood case, this requires converting Doom WAD data to a new format
supported by this new engine.  Work in the engines is divided so that
they can overlap their rendering work as much as possible
(Hatari DSP & CPU profilers help in analyzing that).

In most of other Falcon programs, DSP is used mostly just for handling
background music.  E.g. in demos, MP2 audio de-compression is handled
by DSP.  DSP side itself should work fine, but the exact sync needed
with CPU & DSP side gives some audio quality issues.

Hatari compatibility lists what things need working DSP:
http://hg.tuxfamily.org/mercurialroot/hatari/hatari/raw-
file/tip/doc/compatibility.html#Falcon_software_compatibility_list


	- Eero

> Regards,
> Laurent
> 
> Le 02/06/2015 18:21, Miro Kropáček a écrit :
> > On Tue, Jun 2, 2015 at 6:07 PM, Andreas Grabher
> > <andreas.grabher@xxxxxxxxxxxx <mailto:andreas.grabher@xxxxxxxxxxxx>>
> > 
> > wrote:
> >     Do you think it can be interfaced with the NeXT stuff?
> > 
> > I'll let the technical questions to be answered by the Hatari team but
> > it definitely can by interfaced. Some years ago I took its DSP sources
> > and integrated it into my DSP simulator:
> > https://github.com/mikrosk/cute56 ... easy peasy.
> > 
> > The level of emulation precision is excellent (even for such aged
> > source!), the main source of problems in Hatari comes from CPU <-> DSP
> > sync.