Collecting info on Yamaha FM soundchips

YamahaFM.md

Yamaha GS1 / GS2 (1981)

• GS1: 8 operators per voice: 4 carriers with one modulator each (crossmodulation between 2 modulators), 88-key velocity and poly-pressure sensitive weighted keyboard
• GS2: 4 operators per voice: 2 carriers with one modulator each (crossmodulation between 2 modulators), 73-key velocity sensitive weighted keyboard
• Non-programmable, uses magnetic "voice cards" to load new sounds. Has vibrato, tremolo, ensemble and equalizer controls.
• 2x OPC (YM34501) "Operator-Carrier", 2x OPM (YM34502) "Operator-Modulator", 4x EC (YM322) "Envelope Controller", 4x PG (YM344) "Phase Generator"

Yamaha CE20 / CE25 (1982)

• Uses two 2-op layers per voice (Same as GS2?)
• 2x OP1/OP2 (YM2011) "Operator", 1x PA (YM2010) "Phase Accumulator"

DX7: YM2128(0) (OPS, FM Operator Type-S) and YM2129(0) (EGS)

• mid 1983, the original FM synthesizer, direct predecessor to YM2151/YM2612 etc.
• 16 voices (6-op) (32 in DX1/DX5)
• Used in DX7, DX9 (firmware reduces it to 4-op, 8 algo), TX7, DX1/DX5 (Dual)
• DX9 defines algorithms 1-8 as 1,14,8,7,5,22,31,32 (with removed OP 1 and 2). These algorithms are shared in OPN/OPM/OPZ series.
• Requires two chips, one for operators and one for envelopes

YM2604 (OPS2) and YM3609 (EGM)

• 1986, Used in DX7 mark II, TX802
• 16 voices (6-op)
• Requires two chips, one for operators and one for envelopes

YM2164 (OPP, FM Operator Type P)

• 1985, Used in DX21, DX27, DX100, FB-01, SFG-05, Korg DS-8, Korg 707, IBM Music Feature Card
• 8 voices (4-op)
• The supposedly improved successor to OPM. It is VERY similar. Same pinout and is backwards compatible. In fact, any differences may not affect sound.
• Most differences are probably firmware-bound. For example DX21 has a "Pitch EG" which DX27/100/FB-01 do not. FB-01 has weird stuff like "AR Velocity Sensitivity". This is all probably specific to the firmware and not the chip. Velocity Sensitivity for example is fully controlled in firmware when processing MIDI.

YM2414 (OPZ, FM Operator Type-Z)

• 1987, used in synths TX81Z, DX11, YS100, YS200, PortaTone PSR-6300, PSR-80 and DSR-2000
• 8 channels (4-op), 8 waveforms, two LFOs
• combines the 8 algorithms of YM2151/OPM with 8 waveforms, allowing for sophisticated sounds. Interestingly, borrows the waveform concept from OPL series but uses custom list of waveforms.
• Fixed frequency mode (lock frequency of one or more operators, similar to DX7) (8 Hz - 32640 Hz)

YM2424 (OPZII, FM Operator Type-Z-II)

• 1989, only known to be used in V50 (uses 2xYM2424 for 16 note polyphony)
• 8 channels (4-op), 8 waveforms, two LFOs
• Identical to OPZ but has fixed frequencies down to 0 Hz.

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YMF292 (SCSP)

• 1994, used in Sega Saturn, Sega Model 2/3
• hybrid FM/PCM, uses 32 channels (4-op, but configurable). Mostly PCM was used.

YMF271 (OPX)

• 1993, used in Seibu SPI and Mega System 32 arcade boards
• hybrid FM/PCM, flexible 2/3/4 operators + PCM. Mostly only PCM was used.
• operators can use a unique set of 7 waveforms plus a custom exernal waveform.
• FM: quite unique and flexible. 48 operators (slots), split into 12 "groups". Each group can be configured with 4 "sync" modes (4op mode, 2op x2 mode, 3op + 1?, PCM) 2. 28 algorithms - 4 (2op), 8 (3op), 16 (4op). example: 12 channels with all 4-op, 24 channels with all 2-op. "up to 30 sounds".
• PCM: depending on configuration, PCM can be used extensively; "up to 12 voices".

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OPM

YM2151 (OPM, FM Operator Type-M)

• Year of release: 1983
• FM: 8 channels (4-op)
• Used in: Yamaha CX5M SFG-01 (Yamaha PC, 1983), Arcade, Sharp X1 Turbo (1984), Sharp X68000 (1987)
• Related to: Yamaha YM2164 (aka OPP/FM Operator Type P, derivative used in DX21/27)

Notes

Datasheet. 4 operators per channel, using same algorithms in DX21. The chip is possibly stereo. Channel 3 mode is absent.

Example music

1. BGM - Enduro Racer (1985) (Arcade, YM2151, SegaPCM)
2. Passing Breeze - Out Run (1986) (Arcade, YM2151, SegaPCM)
3. The Heat Waves - Super Monaco GP (1989) (Arcade, YM2151, SegaPCM)
4. Ending - "Last Drive" - Knight Arms: The Hyblid Framer (X68000, YM2151, OKIM6258)
5. Time Attack - GP Rider (1990) (Arcade, YM2151, SegaPCM)
6. Red-Hot Desert - R-Type Leo (1992) (Arcade, YM2151, GA20)
7. Photonic - Room Service (VOPM VST)
8. pedalsteeldrummer - Strawberries and Cream (VOPM VST)
9. Keishi Yonao - Eusion (iYM2151 Demo song)

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OPN

YM2203 (OPN, FM Operator Type-N)

• Year of release: 1984
• FM: 3 channels (4-op)
• SSG: 3 channels (YM2149 PSG(?), register-compatible with AY-3-8910)
• Used in: Arcade, Certain models of NEC PC-6001 (1984)/PC-6601 (1984)/PC-8001 (1985)/PC-8801 (1985)/PC-9801 (1986)
• Related to: YM2608/OPNA (enhanced version of OPN), YM2612/OPN2 (also based on OPN, but no SSG)

Notes

Datasheet. 4 operators per channel, using same algorithms in DX21 and OPM. The chip is possibly mono. Channel 3 has two special modes:

1. Sound effect mode: Allows for individual freq control of each operator, and can mute operators for additional polyphony.
2. CSM (Composite Sine Mode): for speech synthesis (?)

Example music

1. Main Theme - Space Harrier (1985) (Arcade, YM2203 + SegaPCM)
2. Opening - Silpheed (1986) (PC-8801, YM2203)
3. First Step Towards Wars - Ys I: Ancient Ys Vanished (1987) (PC-8801, YM2203)
4. Opening - Dragon Slayer: The Legend of Heroes (1990) (PC-8801, YM2203)
5. Title Theme - Rusty (1993) (PC-9801, YM2203 using special Ch3 mode)

YM2608 (OPNA, FM Operator Type N-A)

• Year of release: 1985
• FM: 6 channels (4-op)
• SSG: 3 channels (YM2149 PSG(?), register-compatible with AY-3-8910)
• ADPCM: 1 channel (8-bit ADPCM format at a sampling rate between 2–16 kHz)
• RHY: 6 channel (enabling playback of six percussion ADPCM samples/"rhythm tones" from a built-in ROM)
• Used in: Certain models of PC-8801 (1985)/PC-9801 (1986)
• Related to: YMF288/OPN3 (stripped down version of OPNA), YM2203/OPN (predecessor), YM2612/OPN2 (very similar, no SSG etc.)

Notes

Datasheet. 4 operators per channel, using same algorithms in DX21 and OPM. The chip is possibly stereo.

Channel 3 has two special modes:

1. Sound effect mode: Allows for individual freq control of each operator, and can mute operators for additional polyphony.
2. CSM (Composite Sine Mode): for speech synthesis (?)

Example music

1. Kono yo no hate de koi o utau Shōjo YU-NO (1996) (PC-9801, YM2608)
2. Only You - Seikimatsu no Juliet to tachi (1995) (PC-9801, YM2608)
3. Level 7 - Revival Xanadu II: Remix (1995) (PC-9801, YM2608)
4. Shout Down - The Scheme (1988) (PC-8801, YM2608)

YM2612 (OPN2, FM Operator type N-2)

• Year of release: 1988
• FM: 6 channels (4-op)
• Used in: Arcade, Sega Mega Drive/Genesis (1988), Fujitsu FM Towns (1989)
• Related to: YM2608 (enhanced version), YM2203/OPN (predecessor)

Notes

SMSPower documentation. Stripped down/low-cost version of YM2608. 4 operators per channel, using same algorithms in DX21 and OPM. Paired with a 4-channel SN76489 on the Mega Drive/Genesis. One FM channel can be converted to 8-bit ADPCM channel. The chip is possibly stereo.

Channel 3 has two special modes:

1. Sound effect mode: Allows for individual freq control of each operator, and can mute operators for additional polyphony.
2. CSM (Composite Sine Mode): for speech synthesis (?)

Example music

1. BGM - Vapor Trail (1991) (Mega Drive, YM2612, No PSG usage)
2. Because You're the Number One - Thunder Force IV (1992) (Mega Drive, YM2612 + PSG)
3. Dreamer - Streets of Rage 2 (1992) (Mega Drive, YM2612 + PSG)
4. Sortie - Gauntlet IV (1993) (Mega Drive, YM2612 + PSG)
5. Reincarnated Soul, Part 2 - Castlevania Bloodlines (1994) (Mega Drive, YM2612, No PSG usage)

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OPL

YM3526 (OPL, FM Operator Type-L)

• Year of release: 1984
• FM: 9 channels (2-op, 1 waveform)
• Used in: C64 Sound Expander and Arcade games (Bubble Bobble)
• Related to: Y8950 (additional ADPCM channels, used in MSX expansion cart)

Notes

Datasheet.

Example music

1. Theme of Terracresta - Terra Cresta (1985) (Arcade, YM3526)
2. Wonder Flight - Wonder Planet (1987) (Arcade, YM3526)
3. Vibrants FM - Edlib OPL2 converted tunes (C64/SFX Sound Expander, YM3526)

YM3812 (OPL2, FM Operator Type-L-2)

• Year of release: 1985
• FM: 9 channels (2-op, 4 waveforms)
• Used in: Arcade, DOS sound cards (Adlib, Sound Blaster etc.), Yamaha keyboards
• Related to: N/A

Notes

Datasheet. OPL-series of chips are 2-op and use different algorithms.

Example music

1. Staff Roll - Street Smart (1989) (Arcade, YM3812)
2. Title - Harald Hårdtand i 'Kampen om de rene tænder' (1992) (DOS, YM3812)
3. Title - Fury of the Furries (1993) (DOS, YM3812)
4. Title Tune - Lollypop (1994) (DOS, YM3812, Edlib)
5. Field 1 - Knights of Xentar (1994) (DOS, YM3812)
6. Battle - Princess Maker 2 (1996) (DOS, YM3812)
7. Vibrants - Fis3 (Edlib)
8. DRAX - Street Wise (Edlib)
9. DRAX - Flash (Edlib)
10. DRAX - Human Nature 1 (Edlib)
11. DRAX - Beyond Minds (Edlib)
12. METAL - Soul Shock (Edlib)
13. METAL - Plastic Session (Edlib)
14. METAL - Introism (Edlib)
15. METAL - Inside the Organ (Edlib)
16. METAL&DRAX - Breaking Wind (Edlib)
17. JO - Drums Are Hard To Do (Edlib)

YM2413 (OPLL, FM Operator Type-L-L)

• Year of release: 1986
• FM: 9 channels or 6 channels/5 drums (2-op, 2 waveforms)
• Used in: Arcade, Yamaha PSS-140/PSS-270
• Related to: JP Master System, MSX/MSX2, VRC7 (6 channel variant used in one NES game: Lagrange Point) (1986-1988)

Notes

Datasheet. Only one channel can be fully programmed. Other must be chose from 15 hard-coded instruments. There are chip variants with different instrument sets, such as YMF281 and YM2423. In general, these are inferior, stripped-down versions of OPL2. TODO: Is there anything programmable? Vibrato and volume? stuff like that.

Example music

1. Out of Rap - F-1 Spirit 3D Special (1990) (MSX2+, MSX-Music/YM2413)
2. Opening Theme - GD: Greatest Driver (1988) (MSX2, YM2413)
3. Theme of Isis - Lagrange Point (1991) (Famicom, VRC7/NES APU)
4. Ending - Fire Hawk (1989) (MSX2, YM2413 + AY-3-8910)

YMF262 (OPL3, FM Operator Type-L-3)

• Year of release: 1988
• FM: 18 channels or 15 channels/5 drums (2-op, 8 waveforms)
• Used in: Arcade, NEC PC-9801, DOS sound cards (Sound Blaster 16 etc.)
• Related to: Yamaha YMF7xx series

Notes

Documentation. Has additional capabilities over OPL2, such as 4 more waveforms, double the channels, and ability to use 4-op instruments. Up to six 4-op instruments can be created, and each take up 2 channels. So that gives you 6 4-op + 6 2-op = 12 at its most extreme. Also, there's a separate mode where you can add drums (similar to OPL2). 6 4-op + 3 2-op + 5 1-op = 14 channels. Many musicians program their own drums in trackers using the full FM mode.

Example music

1. Madbrain - Oskari the Heimfanker (AdlibTracker2)
2. Madbrain - Oskari goes to Soundblasterland (AdlibTracker2)
3. Encore - The Abscence of Julia (AdlibTracker2)
4. Benjamin Gerardin - High Tech Environment III (AdlibTracker2)
5. naruto - MoonDriver for OPL3 DEMO
6. Painful Sigh - Miwaku no Chousho (1995) (PC-9801, YMF262)
7. Sky of the City - Doukyusei 2 (1995) (DOS, YMF262)

YMF278 (OPL4)

• Year of release: 1994
• FM: Exactly the same as OPL3
• PCM: 24 channels of "wavetable synthesis", up to 512 samples, 4 MiB, 16-bit/44.1 kHz
• Used in: Sunrise MoonSound soundcard for MSX (1995), Yamaha Sound Edge soundcard for IBM PC (1995)

Datasheet. In short, this adds high quality sample playback to OPL3. It has hardware envelope support for the samples, an onboard CPU, a 2 MiB ROM full of stock samples, hardware LFO for vibrato/tremolo, stereo panning, among other hardware features. The sample capabilities may be somewhat comparable to YMF292 as used in Sega Saturn. It could also be imagined as the .XM format mixed with OPL3 in one sound chip.

Example music

• naruto - encounter the unknown environment (MoonDriver MSX2+ Demo)
• Dutch Moonsound Veterans - Full Throttle edition

Others

YMU757 / YMU757B (MA-1 / MA-1C)

• Year of release: 1999
• FM: 4 channels (2-op, 2 waveforms)
• Used in: Tons of mobile devices (cell phone, PDA)

Datasheet #1. Datasheet #2. Seems quite limited. 2-op only, but has OPLL's half-sine waveform. Contains a built-in sequencer.

MUL=7, TL=63, AR=15, DR=15, SL=15, RR=15, VIB=1, SUS=1, EGT=1, WAV=1, FB=7

YMU759 (MA-2)

• Year of release: 2000
• FM: 16 channels (2-op, 8 waveforms) or 8 channels (4-op, 8 waveforms)
• ADPCM: 1 channel (4-bit, 4 kHz/8 kHz)
• Used in: Tons of mobile devices (cell phone, PDA)

Datasheet. Boasts much improved FM over MA-1. Appears to have full OPL3 feature set. Contains one very low quality ADPCM channel. Also contains a sequencer. For drum sounds, a single key note can be specified.

MUL=15, TL=63, AR=15, DR=15, SL=15, RR=15, VIB=1, SUS=1, EGT=1, WAV=7, FB=7
+ LFO=3, KSR=1, AM=1, ALG=6, KSL=3, DVB=3, DAM=3

Note: DVB and DAM now have 4 depths instead of the 2 from OPL3.

YMU762 (MA-3)

• Year of release: 2001
• FM: 32 channels (2-op, 29 waveforms) or 16 channels (4-op, 29 waveforms + 3 external waveform)
• PCM/ADPCM: 8 channels (8-bit PCM, 4-bit ADPCM, 48kHz)
• Used in: Tons of mobile devices (cell phone, PDA)

Datasheet. Improved over MA-2. Much improved sample playback. More channels. More operator waveforms. Two extra 4-op algorithms. plus some tweaks to old ones.

MUL=15, TL=63, AR=15, DR=15, SL=15, RR=15, VIB=1, SUS=1, EGT=1, WAV=7, FB=7
+ LFO=3, KSR=1, AM=1, ALG=6, KSL=3, DVB=3, DAM=3
+ XOF=1, EAM=1, EVB=1, PANPOT=31, PE=1

New parameters do the following: EAM (Enable Amplitude Modulation/Tremolo), EVB (Enable Vibrato), XOF (Ignore key-off for Sustain)

YMU765 (MA-5)

• Year of release: 2003
• FM: 32 channels (2-op, 29 waveforms) or 16 channels (4-op, 29 waveforms + 3 external waveform)
• PCM/ADPCM: 32 channels (8-bit PCM, 4-bit ADPCM, 48kHz)
• Used in: Tons of mobile devices (cell phone, PDA)

Datasheet. This uses the same FM synthesis engine of MA-3, but adds a filter called Analog Lite (AL) and a speech synthesis (HV/Humanoid Voice) in Japanese or Korean. Also it bumps up the PCM channel count to 32.

YMU786 / YMU790 / YMU791 (MA-7/ MA-7D / MA-7I)

• Year of release: 2005
• FM: ?
• PCM/ADPCM: ?
• Used in: Tons of mobile devices (cell phone, PDA)

Based on the MA-5's FM synthesis engine. Supposedly has 128 polyphony combined FM and PCM. Has 3D positional sound (AudioEngine), as well as DSP effects (reverb, delay, overdrive etc). 16KB ram instead of 8KB. Can't find much info on it.

YMF825 (SD-1)

• Year of release: 2011
• FM: 16 channels (4-op, 29 waveforms + 3 external waveform)
• Used in: Home appliances (Chinese market)

Datasheet. This appears to be a version of MA-3. It has no PCM or Analog Lite capabilities. Using 2-op instruments does not give extra channels, thus it's probably best to use 4-op instruments.

On the topic of speech/vocal synthesis, the PLG100-SG plugin-in board uses an "OPL" branded chip— the YMF293. The HV-type voices of the MA- series chips sound noticeably similar to the voices produced by the SG board. It uses an onboard dictionary of phonemes. As with the MA-series chips, the functionality of this board was also replicated in software, this was via S-YXG100 Plus.

PLG100-SG official demos
PLG100-SG Owners Manual (archived version, in case it is removed from Yamaha's website in the future).
Info on the SG board @ JavelinArt

--

On a separate note, in addition to many mobile phones, the MA7 chip can also be found in the Yamaha BODiBEAT fitness tracker / music player, which uses an accelerometer and pulse sensor to play music at your current heartbeat / workout intensity level. It is a hybrid generative FM/PCM music player and mp3 player. Here are some examples of the music it produces using the MA7 chip.

Missing YM2610, used in Neo Geo.

For YM2203C, the description says "possibly mono". It IS mono, there is only a single digital output to the YM3014 DAC, which is a mono DAC. There are also no controls for panning (or even assigning L-R channels) in the registers.

For YM2608, it says "possibly stereo". Again, it IS. There are 2 digital data stream outputs to the YM3016 DAC, which is a stereo DAC.

While we are on the subject of DACs, maybe those that are required should be listed. The YM2151 requires the YM3012 stereo DAC. 2608 can use both 3014 (mono) or 3016 (stereo). YM2203 requires 3014.

OPN2 - isn't CSM / "sound effect mode" the same thing? Latter just doesn't use the hardware timer but both allow specific frequencies for all operators on channel 3.

Noticed that the datasheet links are now dead and this doc hasn't been updated in over a year. Is there a simple way to convert this into a github wiki page, so the existing discussion could be retained, but with the ability for others to contribute to it?

@now-its-dark Unfortunately not as a gist. And yeah, datasheetspdf.com shut down its direct pdf links, and now uses a download script. I could update the links but then it would force a download instead of using the browser PDF viewer ☹️.

I'm happy to merge any modified forks, with credit. I just haven't had time to go through everything yet. But if anyone knows of a relevant soundchip or hardware wiki where this sort of article could be expanded by the public, that'd be cool too. This gist started as just a quick way for me to compare/contrast the various FM chip capabilities at a glance. But anyone is free to move it to a dedicated chip wiki and expand on it.

You could use Wayback Machine links, e.g. https://web.archive.org/web/20230915041835/https://pdf.datasheet.live/7b3eefc3/datasheet/YM2203.pdf

@bryc ahh got it, yah I figured it wasn't originally intended to be the public resource which it has has become 😄. This gist shows up in a lot of search results relating to Yamaha chips now.

Totally fair about finding the time, that would be the benefit of a wiki format I guess- easier for others to contribute, without fracturing it or putting the onus on you for any new additions. There are a few places online which might be suitable, but I wonder if just keeping it on gh and creating a wiki based on the data here might accomplish the same thing, since this page already gets a lot of hits— could just point to the wikified version at the top? I'd be happy to help maintain such a thing, if desired.

@akulisch totally! My concern wasn't so much about finding a particular data sheet myself, but rather because this doc is a good resource, just wanted to flag it.

@now-its-dark @bryc
I'd be happy to set up a wiki for Yamaha chips, or something similar. That's if there isn't already a better sound chip wiki out there. If you'd like me to set something up, let me know.

I'm also happy to provide datasheets for various Yamaha chips, which I have collected quite a lot.

…

------------------ Original ------------------ From: Anthony ***@***.***> Date: Wed,Jun 12,2024 8:55 AM To: ajxs ***@***.***> Cc: Comment ***@***.***> Subject: Re: bryc/YamahaFM.md @ajxs commented on this gist. @now-its-dark @bryc I'd be happy to set up a wiki for Yamaha chips, or something similar. That's if there isn't already a better sound chip wiki out there. If you'd like me to set something up, let me know. — Reply to this email directly, view it on GitHub or unsubscribe. You are receiving this email because you commented on the thread. Triage notifications on the go with GitHub Mobile for iOS or Android.                                                            

May I suggest... Wikipedia?
There's some others out in the wild,
https://vgmrips.net/wiki/Category:Sound_Chips
https://www.vgmpf.com/Wiki/index.php?title=Category:Chip
But Wikipedia reigns supreme -
https://en.wikipedia.org/wiki/List_of_sound_chips

Wikipedia is good. My only reservation is that Wikipedia articles aren't supposed to be too technical, right? What makes a database of Yamaha's FM chips useful is really all the technical minutiae. Wikipedia doesn't seem like a good place to put register maps, or programming guides. I know that this gist doesn't have either, but a wiki could have those things.

You probably should clearly mention fixed freq mode for OPZ if it's really confirmed

@LTVA1 added Fixed mode info to OPZ, thanks!

You would also need to add info about CSM mode for OPN, OPN2, OPNA, OPNB, OPNB2. In CSM mode each time Timer A overflows the phase of all operators on extended channel (channel 3 or 2, depending on the chip) is reset. Their envelope is reset to and forced into release phase, so you can control this strange repeating envelope with release rate. This mode allows you to have basically 5 frequencies on the same channel (apart from harmonics and such; with algorithm 7 you have Timer A as fundamental frequency, and 4 more frequencies from operators, plus harmonics from envelope and feedback on 1st operator). With proper adjustment it kinda resembles human sounds, and by changing Timer A frequency and operators settings you can make... uh... something like speech. By the way, from my fiddling with MA-7 authoring tool, the same principle in used in MA-7 (if we trust Yamaha's MA-7 emulator), although, with 8 operators, filtering and more waveforms (I am not sure if speech synth has dedicated hardware channels or it's done somehow on FM channels).

I have also found about OPM having CSM mode, although, unlike OPNx, it does the phase and envelope reset for all operators on all 8 channels.

I found more detailed datasheet, although the scan quality isn't great, so please add a link as a second datasheet or whatever. https://ltva1.github.io/OPM/ym2151_synthesis.pdf

Also OPN2's 6th channel in sample moed is NOT ADPCM, it's just a dumb 8-bit DAC where you feed the values via CPU. It depends on CPU stage whether it's ADPCM decoded into PCM stream or plain PCM info.

OPNA ADPCM-B channel has sampling frequencies between 2kHz and 55.5kHz on default clock speed. The same applies to OPNB/OPNB2. 2-16 kHz is the sampling rate, for sampling external signal.

http://nemesis.hacking-cult.org/MegaDrive/Documentation/YM2608J%20Translated.PDF

OPNB is YM2610, OPNB2 is YM2610B. In short, OPNB is like OPNA, but rhythm channels can now play arbitrary samples at fixed sample rate (around 18 kHz?). OPNB has only 4 FM channels, with extended mode applicable to channel 2. OPNB2 is the same as OPNB but the FM part is restored as in OPNA (6 FM channels, 3rd one can be in extended mode).

OPNA, OPN, OPNB, OPNB2 feature CSM mode for extended channel. OPM/OPL1/OPL2 feature CSM mode but on all channels at the same time.

OPNB is YM2610, OPNB2 is YM2610B. In short, OPNB is like OPNA, but rhythm channels can now play arbitrary samples at fixed sample rate (around 18 kHz?). OPNB has only 4 FM channels, with extended mode applicable to channel 2. OPNB2 is the same as OPNB but the FM part is restored as in OPNA (6 FM channels, 3rd one can be in extended mode).

OPNA, OPN, OPNB, OPNB2 feature CSM mode for extended channel. OPM/OPL1/OPL2 feature CSM mode but on all channels at the same time.

OPNB Adpcm B can go from 2 to 55KHZ and the ADPCM-A channels (the ones that were the ym2608 rhythm channels) play at 18.5KHZ at the standard 8MHZ clock speed.

Yes