Maybe some new technical information about the Yamaha YM2612

For anything related to sound (YM2612, PSG, Z80, PCM...)

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Asagoth
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Maybe some new technical information about the Yamaha YM2612

Post by Asagoth » Sun Jul 30, 2017 11:06 am

Hello SpritesMind... i'm new here... so sorry if i'm doing something wrong i just want to share a Japanese book that i found in the net a few days ago... here http://retrocdn.net/File:FM_TOWNS_JP_Te ... a_Book.pdf ... is a Technical Book for the FM TOWNS system... as you know this computer has the same YM2612 sound chip as the Mega Drive/Genesis... from pages 218 to 241 has a lot of technical information about the chip... i showed this to a person who has knowledge on Japanese language and the chip and that person assured me that the info in this book his better than the Sega Docs or the Yamaha YM2608 documentation...the book needs translation though ...I think someone should see this.Thanks for the attention...

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Sik
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Re: Maybe some new technical information about the Yamaha YM2612

Post by Sik » Mon Jul 31, 2017 8:02 am

Asagoth wrote:
Sun Jul 30, 2017 11:06 am
i showed this to a person who has knowledge on Japanese language and the chip and that person assured me that the info in this book his better than the Sega Docs or the Yamaha YM2608 documentation...
I meant that it explains things better =P Actually has details about how all the values affect the sound instead of a quick overview (there are even tables indicating how long it takes for envelopes to go mute for every possible decay value). And actually explains how FM works (i.e. where the phase modulation is applied and how it's fed into each operator). It's absurdly in-depth as far as programming manuals go.

I don't think there's anything new though. Once the YM2612 got decapped pretty much everything was visible.
Sik is pronounced as "seek", not as "sick".

Asagoth
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Re: Maybe some new technical information about the Yamaha YM2612

Post by Asagoth » Mon Jul 31, 2017 8:48 am

Oh... ok... I misinterpreted you ... sorry... now is better explained... thank you... It's a pity that it was not discovered earlier....

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TmEE co.(TM)
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Re: Maybe some new technical information about the Yamaha YM2612

Post by TmEE co.(TM) » Mon Jul 31, 2017 9:53 am

Outside of telling how the phase modulation works and the tables there isn't anything new there. I does mention test registers explicitly though, but no extra info haha.
Values in the tables aren't very useful for MD though, because the YM runs at 8MHz there, so all the values are slightly too big. Sega docs also have the values based on 8MHz clock and not (53.203424 / 7) or (53.693175 / 7).
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Asagoth
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Re: Maybe some new technical information about the Yamaha YM2612

Post by Asagoth » Mon Jul 31, 2017 11:13 am

That's why I said "maybe"... i'm not a "Tech Guy" just a curious one... I just wanted to share this ... i hope it helps on something...

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Re: Maybe some new technical information about the Yamaha YM2612

Post by TmEE co.(TM) » Mon Jul 31, 2017 11:28 am

It is definitely cool stuff, thänk you for digging it up ~
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Re: Maybe some new technical information about the Yamaha YM2612

Post by Asagoth » Mon Jul 31, 2017 12:18 pm

No need to thank me ... I was just lucky to find this.Those "Engrish" words on the page 218 "FM MODURATION" and "YM2612" caught my attention :lol: ...

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Re: Maybe some new technical information about the Yamaha YM2612

Post by Sik » Mon Jul 31, 2017 2:40 pm

TmEE co.(TM) wrote:
Mon Jul 31, 2017 9:53 am
Outside of telling how the phase modulation works and the tables there isn't anything new there. I does mention test registers explicitly though, but no extra info haha.
Values in the tables aren't very useful for MD though, because the YM runs at 8MHz there, so all the values are slightly too big. Sega docs also have the values based on 8MHz clock and not (53.203424 / 7) or (53.693175 / 7).
I'm not even sure if the decay tables are really useful anyway since the durations specified in them only make sense when the decay starts from the peak (otherwise they last shorter). The other tables make more sense since they deal with frequency and the values are relative (e.g. how many cents are added).

Still, I'd assume that the circuit used to compute all this is already visible from the decap shots, right?
Sik is pronounced as "seek", not as "sick".

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