atari800 Pokey emulation

[ivop]

Hi,

 

I was thinking about fixing the Pokey emulation of atari800. So, can anybody tell me exactly which sounds and features are not emulated properly and how to produce them on real hardware?

 

Thanks,

--Ivo

[phaeron]

2.2.0rc1:

• IRQs only fire with scanline precision.
  
• Two-tone mode doesn't affect IRQs.
  
• Asynchronous receive mode doesn't suspend timers 3 and 4 (POKE 53775,19).
  
• Initialization mode isn't implemented (POKE 53775,0 should kill non-1.79MHz audio).
  

[analmux]

I don't use the unix based emu, but does it already include 2tone-filter features?

 

About 2tone-fiter: It's an extended sound setting. Writing value #$8B to $D20F (SKCTL) will force sync mode: Pokey channel 1 will be synced by channel 2. Application: keep channel 2 silent (but not really needed) and use AUDC1 to specify a desired type of sound.

 

And, another thing: Pokey triangle wave feature (or, even better: "artefact"). In theory, the basic feature (or 'bug') causing triangle wave is based on the nonlinear (final) mixing of the audio signals of the 4 channels. Maybe you should contact Perry M.

 

So, if the nonlinear mixing is included, then triangle wave, but also other similar features, will automatically roll out.

[analmux]

Oops, it seems to be already added:

 

729 2008-05-07  Perry McFarlane  <perry_m@fastmail.fm>
730 * mzpokeysnd.c, configure.ac, pokey.h, pokeymix.inc: Nonlinear mixing,
731   two-tone filter, corrected STIMER.

 

However, I'm not sure whether this change is 'activated' yet.

[ivop]

Oops, it seems to be already added:

 

729 2008-05-07  Perry McFarlane  <perry_m@fastmail.fm>
730 * mzpokeysnd.c, configure.ac, pokey.h, pokeymix.inc: Nonlinear mixing,
731   two-tone filter, corrected STIMER.

 

However, I'm not sure whether this change is 'activated' yet.

 

I see. It is not enabled by default I guess, but with --enable-nonlinear_mixing it should work.

 

So, does that mean that everything works like it should (except for the IRQ timing)? I remember emkay repeatedly saying this or that does not sound correct on emulators.

[Kr0tki]

Hello, I'm also working on improving POKEY emulation in Atari800. I'm doing it as a part of my A8CAS project (I need cycle-exact IRQ emulation for loading some tapes). Currently I've only fixed the two-tone filter emulation (it is incorrect in Atari800 currently) and implemented asynchronous mode timer suspending (although it's not 100% exact right now).

 

If you'd like to check my work out, got to http://a8cas.sourceforge.net/ and grab the newest version of liba8cas and atari800 from the Git repository.

 

I remember emkay repeatedly saying this or that does not sound correct on emulators.

There are multiple reasons for Emkay's grief

- He (and pretty much everybody else) uses Atari800WinPLus, which is pretty outdated compared to Atari800;

- Raster Music Tracker also has broken POKEY emulation, AFAIK;

- The "Synchronised sound" feature of Atari800 is relatively new and was not in the last release of the emulator.

[carmel_andrews]

Hello, I'm also working on improving POKEY emulation in Atari800. I'm doing it as a part of my A8CAS project (I need cycle-exact IRQ emulation for loading some tapes). Currently I've only fixed the two-tone filter emulation (it is incorrect in Atari800 currently) and implemented asynchronous mode timer suspending (although it's not 100% exact right now).

 

If you'd like to check my work out, got to http://a8cas.sourceforge.net/ and grab the newest version of liba8cas and atari800 from the Git repository.

 

I remember emkay repeatedly saying this or that does not sound correct on emulators.

There are multiple reasons for Emkay's grief

- He (and pretty much everybody else) uses Atari800WinPLus, which is pretty outdated compared to Atari800;

- Raster Music Tracker also has broken POKEY emulation, AFAIK;

- The "Synchronised sound" feature of Atari800 is relatively new and was not in the last release of the emulator.

 

 

 

 

 

Reason why that emulator is outdated is due to the fact that it has not been updated in ages and since then other emulations have come on that have superceeded that emulator

[Kr0tki]

The above sentence should be placed in dictionaries under the "Truism" entry, as an example.

[Divya16]

Hello, I'm also working on improving POKEY emulation in Atari800. I'm doing it as a part of my A8CAS project (I need cycle-exact IRQ emulation for loading some tapes). Currently I've only fixed the two-tone filter emulation (it is incorrect in Atari800 currently) and implemented asynchronous mode timer suspending (although it's not 100% exact right now).

 

If you'd like to check my work out, got to http://a8cas.sourceforge.net/ and grab the newest version of liba8cas and atari800 from the Git repository.

 

I remember emkay repeatedly saying this or that does not sound correct on emulators.

There are multiple reasons for Emkay's grief

- He (and pretty much everybody else) uses Atari800WinPLus, which is pretty outdated compared to Atari800;

- Raster Music Tracker also has broken POKEY emulation, AFAIK;

- The "Synchronised sound" feature of Atari800 is relatively new and was not in the last release of the emulator.

 

 

 

 

 

Reason why that emulator is outdated is due to the fact that it has not been updated in ages and since then other emulations have come on that have superceeded that emulator

 

Isn't it written in the 21st century so why would it need that much updating? Computers have just gotten faster recently; the colors, resolution, graphics memory, more sound channels, etc. shouldn't affect the Atari emulation.

 

Or are you just talking about bugs that were discovered after its last release?

[phaeron]

I've got another one to add: it seems that Atari800 outputs an audio stream with a significant DC bias. On Windows XP, this causes the main sound output to distort if any other sound is also playing at the same time, even if the emulated Atari program isn't playing any interesting sounds. It's not really a POKEY emulation issue, but I thought I'd bring it up regardless.