Re: [hatari-devel] DSP issue on M1 Mac (not happening on x86_64)

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Le 28/12/2022 à 15:02, Andreas Grabher a écrit :
> > Am 28.12.2022 um 14:54 schrieb Nicolas Pomarède <npomarede@xxxxxxxxxxxx>:
> >
> > Le 28/12/2022 à 14:49, Andreas Grabher a écrit :
> > > Hello all,
> > > this issue affects Previous, but because Previous shares most of its DSP simulation with Hatari (with minor additions like DMA) it might also affect Hatari. In some DSP music demo I am getting a cracking noise when running on an M1 Mac. Running on an x86_64 Mac there very same demo does not suffer from that noise.
> > > Did someone experience a similar issue using Hatari on an M1 Mac? Does someone have an idea where to start searching the bug?
> > > Best wishes,
> > > Andreas
> >
> > Hi
> >
> > can't tell if there're some cracking noises under Hatari recently.
> >
> > but the DSP / crossbar part uses some floating point variables to mix the different frequencies into the final audio stream. If there's not enough precision this can give bad rounding and artefacts in the sound.
> >
> > Maybe M1 mac has different precision for float/double ?
> Only the DSP core is used (dsp_core.c, dsp_cpu.c and dsp_disasm.c). As far as I can tell they do not use any floating point numbers.

indeed, only use of double's is in crossbar.c
falcon uses crossbar.c for outputing sound, if next/previous has some 
different HW that only use the DSP core I'm not sure this can be duplicated.

Nicolas