Re: Best way to play samples on *both* 8580 and 6581
                                       
   From: Nate / DAC <natedac@southwind.net>
   Reply to: Nate / DAC
   Date: Sat, 26 Sep 1998 01:14:07 -0500
   Organization: SouthWind Internet Access, Inc.
   References:
          <6ugqc7$8ck@chronicle.concentric.net>

> I'm writing drivers to play back PCM on the 64. Writing for the 6581 is
> easy, but of course sounds like dreck on the 8580. Someone have a routine
> or quick hack to play back a pulse on an 8580, given an amplitude?

Well this depends on whether you are trying to play 4-bit samples or 8-bit
samples.

If you're playing 4-bit samples, simply wipe all registers with 0's, then
set $D406 to #$F0, and set $D404 to #$41, to enable the 8580 volume fix.

If you're playing 8-bit samples, play them as you normally would on a 6581,
and simply adjust the filter cutoff frequency.

To detect the type of SID chip, I am told you are supposed to select a
waveform on voice 3 that only the 8580 can reproduce, and read the OSC-3
output register.  The 6581 will return abnormally low-values, while the 8580
will return a wide range of values..  Perhaps you are supposed to take a few
hundred samples and create an average?

I opted to place this 4-bit volume fix option as a user-selectable feature
in my programs.

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