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I wonder how difficult it would be to re-create it in software? It'd be cool to emulate it similar to tlb's XAnalogTV. https://github.com/katahiromz/XScreenSav

I wonder how difficult it would be to re-create it in software? It'd be cool to emulate it similar to tlb's XAnalogTV. https://github.com/katahiromz/XScreenSaverWin/blob/master/non-wgl/analogtv.c https://github.com/katahiromz/XScreenSaverWin/blob/master/no... https://www.youtube.com/watch?v=_ODQ_lHRMXo https://www.youtube.com/watch?v=_ODQ_lHRMXo

khedoros1 10y ago
MAME's implementation shows 5 contributors. Maybe you could ask them? https://github.com/mamedev/mame/blob/master/src/devices/sound/sn76477.cpp https://github.com/mamedev/mame/blob/master/src/devices/soun... https://github.com/mamedev/mame/blob/master/src/devices/sound/sn76477.h https://github.com/mamedev/mame/blob/master/src/devices/soun...
- buzzybee 10y ago
  AFAIK MAME's accuracy leaves a lot to be desired with respect to anything involving analog signal paths. For example, the sound system used in the Sente SAC-1 hardware is based on the CEM3394 chip, also seen in several pro synths of the era. The emulation does play sound, but last I checked, there wasn't any filter emulation, so it poorly represents the audio of those games. Edit: And I wouldn't expect the situation to change soon. Accurate analog emulation is something commercial VST plugin makers have been working on for years, and they've come "close enough for most people", but the time spent on algorithm development and optimizing CPU usage is quite high.
squarefoot 10y ago
Not easy, as would be even recreating it in hardware. This is the analog world where tolerances, stray capacitance and unpredictable small differences in gain or frequency response make every circuit behaviour slightly different even though it uses the same exact parts and layout. A good enough digital recreation of that circuit would be possible only if it could sample the imperfections of a real chip, and to be believable it should probably analyze a hundred chips to get what parameters are changed during production and how much.
femto 10y ago
That was my first thought too. My second thought was that the most effective recreation would be to build a SPICE model [1], and whether that SPICE model could run in near real time on a modern CPU. A simple SPICE model should be straightforward based on the circuits in the article. From memory, the SPICE transistor models take things such as transistor feature sizes as parameters, so it might be possible to get a surprisingly accurate model from the die photo? [1] https://en.wikipedia.org/wiki/SPICE https://en.wikipedia.org/wiki/SPICE

khedoros1 10y ago

MAME's implementation shows 5 contributors. Maybe you could ask them? https://github.com/mamedev/mame/blob/master/src/devices/sound/sn76477.cpp https://github.com/mamedev/mame/blob/master/src/devices/soun... https://github.com/mamedev/mame/blob/master/src/devices/sound/sn76477.h https://github.com/mamedev/mame/blob/master/src/devices/soun...

buzzybee 10y ago
AFAIK MAME's accuracy leaves a lot to be desired with respect to anything involving analog signal paths. For example, the sound system used in the Sente SAC-1 hardware is based on the CEM3394 chip, also seen in several pro synths of the era. The emulation does play sound, but last I checked, there wasn't any filter emulation, so it poorly represents the audio of those games. Edit: And I wouldn't expect the situation to change soon. Accurate analog emulation is something commercial VST plugin makers have been working on for years, and they've come "close enough for most people", but the time spent on algorithm development and optimizing CPU usage is quite high.

squarefoot 10y ago

Not easy, as would be even recreating it in hardware. This is the analog world where tolerances, stray capacitance and unpredictable small differences in gain or frequency response make every circuit behaviour slightly different even though it uses the same exact parts and layout. A good enough digital recreation of that circuit would be possible only if it could sample the imperfections of a real chip, and to be believable it should probably analyze a hundred chips to get what parameters are changed during production and how much.

femto 10y ago

That was my first thought too. My second thought was that the most effective recreation would be to build a SPICE model [1], and whether that SPICE model could run in near real time on a modern CPU. A simple SPICE model should be straightforward based on the circuits in the article. From memory, the SPICE transistor models take things such as transistor feature sizes as parameters, so it might be possible to get a surprisingly accurate model from the die photo? [1] https://en.wikipedia.org/wiki/SPICE https://en.wikipedia.org/wiki/SPICE