louisg Posted January 11, 2019 Share Posted January 11, 2019 (edited) I've recently become fascinated, again, with early software synthesis. For example, take Eugene Jarvis' sound engine in Robotron and Defender: I love that it ran on such a limited processor. But the thing that really gets me as a synth geek is the parameter space-- the fact that you can do so much with what I think he said was 8 parameters (in the Robotron GDC post-mortem). I see that he goes into a little more detail here: http://www.firepowerpinball.com/downloads/Eugene_Jarvis_Interview.pdf-- it's funny too because we always think of general-purpose-CPU softsynths as a late 90s phenomenon! Now, I see someone has done a commented Robotron disassembly, but I don't think they got to the sound system. I'd love to find more info about it, short of disassembling it myself. I also noticed that Konami's Time Pilot '84 produces a lot of similar tones. It supposedly uses one of those simple squarewave+noise PSGs, but it's driven by a reasonably fast CPU, which makes me wonder what's really going on there. Maybe it's manipulating the sound chip's registers really fast, or there's a bit-bang channel in addition to the sound chip. I think some of those dedicated PSGs had simple amplitude envelopes you could leverage, too..? Any other arcade games that use or are suspected of using a softsynth to generate their sounds besides these and the Namco games? Any tones that strike you as particularly neat? I might play with some primitive softsynth concepts tonight. I want to see if I can make one that barely branches, and also see what FM does with such low resolution grainy tables (for example, do you really need a LFSR if you've got FM feedback?). Edited January 11, 2019 by louisg Quote Link to comment Share on other sites More sharing options...
louisg Posted January 12, 2019 Author Share Posted January 12, 2019 (edited) So far, I'm finding that an 8-bit counter for frequency isn't enough at 22khz when indexing into a 64-byte waveform (so, 8-bit counter waveform position >> 3). I'm guessing these systems used 16-bit counters. FM feedback wasn't so hot with such simple waves-- some kind of rng is definitely needed for noise fx. Edited January 12, 2019 by louisg Quote Link to comment Share on other sites More sharing options...
louisg Posted January 12, 2019 Author Share Posted January 12, 2019 I just found this! It looks like a pretty promising recreation of the sound routine: http://www.lomont.org/Software/Misc/Robotron/ Quote Link to comment Share on other sites More sharing options...
griz Posted February 26, 2019 Share Posted February 26, 2019 Super cool. I've got a Defender upright. Such classic sounds. Quote Link to comment Share on other sites More sharing options...
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