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