<infodump>
'OPS' series
ym2128/ym2129:'OPS' and 'EGS': ?16? channels of 6-operator FM synthesis with all the features of the OPM and more. undocumented, needs reverse-engineering for mess.

'OPM' series
ym2151:'OPM' 8 channels of 4 operator FM synthesis with LFO, detune, and other fun features. Uses an external DAC for output.
ym2164:'OPP' same as ym2151 but with multitimbre (channel linking? multiple notes per channel? not sure) stuff; undocumented, needs reverse-engineering for mess. Uses an external DAC for output.
ym2414(B):'OPZ', similar to ym2151 but allows source waveform for each channel to be selected as one of 8 waveforms much like the opl3, instead of being fixed as sine. undocumented, needs reverse-engineering for mess. Uses an external DAC for output.

'OPN' series
ym2203:'OPN' basically an SSG (read: ay-3-8910 clone) with added 4-op fm synthesis; 3 channels of FM; does not have LFO, but supports almost everything else the OPM does. has two (or three?) 8-bit i/o ports. Uses an external DAC for output.
ym2608:'OPNA' an OPN with 6 channels of FM instead of 3, SSG, and an adpcm BUS for encoding/decoding adpcm. has one 8-bit i/o port. Uses an external DAC for output; Stereo; Has internal ?adpcm? samples for Rhythm instruments.
ym2610(B):'OPNB' an OPN with 4 channels (B version has 6 channels) of FM instead of 3, SSG, and a DUAL adpcm bus for encoding/decoding adpcm (simultaneously?). has no i/o ports. Uses an external DAC for output; Stereo; Has internal ?adpcm? samples for Rhythm instruments.
ym2612:'OPN2' an OPN with 6 channels of FM instead of 3, NO SSG channels, and an adpcm channel sharing the time-slot of the last FM channel. Stereo Internal DAC, time-multiplexed output (i.e. the 6 channels are not pre-mixed and then sent to DAC, but 'rendered' in sequence to the DAC rapidly);
ym3438:'OPN2C' same as OPN2, but CMOS instead of NMOS. Uses much less power and hence runs cooler. Cannot usually be used as a replacement for the OPN2 as its inputs are ?not TTL compatible?(ask Charles Macdonald about this). Supposedly fixes two bugs in the OPN2: the sine wave 'downward slope portion' is no longer 1 unit too high; the dac no longer powers down (causing noise/clicks) when it hits exactly 0.000.

'OPL' series
ym3526:'OPL' 2-op FM synthesizer with 9 channels of FM; sine wave as source waveform only. Has 3 rhythm channels which can double as FM. Relatively limited compared to OPM/OPN (no detune, no SSG-EG, etc) but has many channels. SUPPOSEDLY has the same 'downward slope portion' bug as OPN2 does. Uses an external DAC.
ym3812:'OPL2' 2-op FM synthesizer with 9 channels of FM; pin-compatible and register compatible with ym3526, only addition is now has 4 different source waveforms (sine, rectified/absolute sine, half-period sine, and rising-portion-of-absolute-sine-wave-only sine. Still has the 'downward slope portion' bug. Uses an external DAC.
ym2413:'OPLL' 2-op FM synthesizer with 9 channels of FM; more or less an OPL2 with only 2 source waveforms and most (but not all) of the extra features stripped out; has 15 fixed instruments from internal rom (needs decapping) usable, and one user-controllable instrument. No CSM mode. Internal DAC, time-multiplexed output (i.e. 6 of the 9 channels are not pre-mixed and then sent to DAC, but 'rendered' in sequence to the DAC rapidly; the remaining 3 channels come out a separate pin, with their own DAC, or possibly multiplexed from the same main DAC) NOTE: the Konami VRC7 chip is an NES mapper chip with an on-die clone or licensed copy of the ym2413; it has a (mostly) different instrument rom, does not support the rhythm channels, and has only 6 fm channels instead of 9.
ymf262L:'OPL3' 2-op/4-op FM synthesizer with 18 channels of FM; pretty much an enhanced OPL2 with twice as many channels. No CSM mode. Uses an external DAC. Requires a clock running at 4 times the speed that the other Yamaha chips run at. Has a 4-op mode which yields 6 channels of 4 op, 6 channels of 2 op. Stereo. Has internal DAC, unknown if it is multiplexed or not but it wouldn't surprise me.

Some later chips exist which are single chip implementations of OPS/EGS, a chip called OPN3 which I have no info on, and another chip which is a combination of an OPL3 and an OPN3 on one chip. I have very little information about any of these. They all have YMFxxx numbers.
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In short:
Most OPM instruments EXCEPT THOSE THAT USE LFO can be losslessly converted to OPN instruments. Some can be converted to the 4-op OPL3 format but this is lossy as OPL3 doesn't support detune and some other features like SSG-EG.
Pretty much everything can be converted to OPZ instruments, but those chips are very rare.

LN

Last edited by Lord Nightmare; 02/18/09 01:01 AM. Reason: update stuff from knurek

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