info on Yamaha YM2164 FM(?) chip?

[edanderson]

I recently picked up a Korg 707 synth for cheap, and I was hoping to do some kind of simple mods to it.  A best I can tell, this digital FM beastie has this Yamaha YM2164 4-op FM chip as its heart, chained up to a YM3012 DAC.  Does anyone know anything about how this synth works.  All I've been able to dig up so far is a pinout of the DAC.

I was hoping to perhaps do some kind of decimator mod (chop the least significant bits off for extra grunge-effect) but since the DAC input is (AFAIK) a serial stream this seems like it might be difficult.

Any thoughts, or should I just paint the case and be done with it?

Thanks,

Ed Anderson