cr1901 changed the topic of ##yamahasynths to: Channel dedicated to questions and discussion of Yamaha FM Synthesizer internals and corresponding REing. Discussion of synthesis methods similar to the Yamaha line of chips, Sound Blasters + clones, PCM chips like RF5C68, and CD theory of operation are also on-topic. Channel logs: https://libera.irclog.whitequark.org/~h~yamahasynths
<Lord_Nightmare>
it might just be a bug in the older one
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<ValleyBell2>
I remember someone (maybe Nuke.YKT) saying, that the two disabled FM channels are physically present but not connected.
<ValleyBell2>
He definitely had a look at the YM2610 some time ago. There is a " Nuked-OPNB
<tunixman>
yeah, I'd imagine they're just disconnected... didn't pass binning.
<tunixman>
hm, I wonder what would happen if it were two different channels that failed...
<andlabs>
honestly it sounds intentional to me
<andlabs>
the OPN chips are built in a very specific lego-block-y way; they are always sets of 3 identically-configured OPN channels
<qu1j0t3>
yeah, i was thinking it's either artificial product segmentation, or yield recovery (good)
<andlabs>
YM2203: one set of 3 channels
<andlabs>
YM2608: two sets of 3 channels
<andlabs>
YM2610/2610B: two sets of 3 channels
<andlabs>
YM2612: two sets of 3 cahnnels
<andlabs>
always two normal channels and one CSM channel with idependently programmable operator frequencies
<tunixman>
oh yeah that's definitely more likely than whatever I was thinking.
<tunixman>
laser-drill the selector bits based on testing haha
<andlabs>
although on the YM2612 the second set of FM channels has that feature disabled and a direct DAC input is provided instead
<andlabs>
I don't know of any other OPN chips or what they provide
<andlabs>
just not allowing access to one of the channels would be much easier to implement
<andlabs>
though fi it was me I would have called that model the B model instead
<andlabs>
IDK
<andlabs>
and apparently Yamaha were extremely controlling of who would be able to buy what chip
<andlabs>
they would have had a vested interest in doing that
<andlabs>
but again, why would they introduce the compromised version later? I have to actually figure out what devices shipped with the 2610 before 1990
<Sarayan>
'b' is the version with more channels...?
<andlabs>
yes
<andlabs>
or rather, with no channels disabled
<Sarayan>
yeah, probably. But I don't see how it matches with "compromised version later"
<andlabs>
if we just go by arcade games that I can find the YM2610B was first used on Taito games from 1998
<andlabs>
the YM2610 was used on the Neo Geo
<andlabs>
so I'm missing some piece of hardware
<Sarayan>
neogeo is not 2612?
<andlabs>
no
<Sarayan>
ah no, megadrive
<andlabs>
actually no
<andlabs>
vgmrips is wrong
<andlabs>
the ninja warriors and darius 2 use a YM2610, not a YM2610B
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<andlabs>
does google reverse image search ever actually find any matches or does it just do a vague guess and give up instantly, throwing in a totally unrelated search term to compensate