TIL that the Yamaha YM3812 (OPL2) is clocked at 3.579MHz but emits (digital, floating-point!) samples at a rate of 49716Hz.
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I'm gonna go out on a limb here and speculate that the fact that they're doing a 72x clock subdivision and that this thing has 18 (table ROM-driven) oscillators (18*4=72...) is probably not just a coincidence. :)
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the other fun thing is that absolutely everything in this chip is log or semilog-scale, including the sine tables (which IIRC store -log(sin(x))), and all the additions I can find anywhere in the whole thing happen after all the multiplications
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in short I'm pretty sure there's not a single multiplier anywhere in that design, it's probably all just adds, then at some point exp table lookups, and then more adds
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yuuup sure looks like ithttps://docs.google.com/document/d/18IGx18NQY_Q1PJVZ-bHywao9bhsDoAqoIn1rIm42nwo/edit …
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Fabian Giesen Retweeted Olivier Galibert
more notes herehttps://twitter.com/o_galibert/status/1200719370764374017 …
Fabian Giesen added,
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Yep, these chips are amazing in the amount of musicality per gate of logic. I did a bunch of reverse engineering work for what is now dexed; unfortunately it isn't written up very well.
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