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PostPosted: Sun Apr 22, 2012 7:21 pm 
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But they are not from the same box - date codes are different :?


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PostPosted: Tue May 22, 2012 4:30 pm 
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Now I finally got some sound out of one of these chips...

As Kevtris mentioned on his document for VRC7 it does work exactly as a YM2413. The only difference is that there's no percussion output and a few of the internal voices are different (probably to accommodate the fact that it miss the percussion pin on the package.

Image

Image

Image

"schematics" on how to make it operate like a YM2413 will follow in a short while (once I make the block representation for the chip on BVPE3)...

If anyone is curious, I just wired it so it would see only $9010/$9030 writes, connected the "A5" of the would be Famicom to the MSX A0,M2 to the /RESET and wired /WR and /CS to the original YM2413 connector. The chip is running from a 3.57 mhz quartz crystal instead of a ceramic resonator.

Sound is slightly different than that of a normal YM2413 due to the subtle internal rom differences and lack of percussion.

edit: Repaired picture links.


Last edited by l_oliveira on Thu Jul 24, 2014 3:54 pm, edited 1 time in total.

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PostPosted: Wed May 23, 2012 4:25 pm 
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Requesting clear photo of PCB, where is PCB with VRC7 connected.


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PostPosted: Wed May 23, 2012 5:34 pm 
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80sFREAK wrote:
Requesting clear photo of PCB, where is PCB with VRC7 connected.


This one ?
Image

Or the one with the VRC7 chip itself ?

edit: Repaired picture links.


Last edited by l_oliveira on Thu Jul 24, 2014 3:55 pm, edited 1 time in total.

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PostPosted: Thu May 24, 2012 5:35 am 
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No, no, this one. Nice! :D Hows YM2203 sounds? I have one, but untested yet(desoldered from sound card looking board).


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PostPosted: Thu May 24, 2012 5:37 am 
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YM2203 is a half channels of YM2612 (Sega Genesis) with minor differences, they are software compatible for the most part and sounds the same.


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PostPosted: Thu May 24, 2012 6:46 am 
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Shiru wrote:
YM2203 is a half channels of YM2612 (Sega Genesis) with minor differences, they are software compatible for the most part and sounds the same.


Actually YM2203 is the original chip that started the OPN family, which is in turn a merge of a "cheapened" OPM (YM2151) core with a SSG (YM2149F which is Yamaha's own version of the legendary AY-3-8910 sound chip from the Intellivision)...

The chip on the Mega Drive in particular is two YM2203 slapped together with some additional interconnection to allow for 4-op voices using the 2 FM cores simultaneously. Ah and SSG stuff got mostly removed keeping only the envelope registers. I suppose, as these are used by the FM synth to enhance the chip features.

There's even tools to translate/convert patches from OPM to OPN or the inverse ... (edit: oy I forgot, you made the tools, Shiru XD my bad)

The VRC7 is a member of the OPL family in the other side, so it uses YM3526 (OPL)/YM3812(OPL2) patches/tones.

The board I posted pictures from contains also an Konami 051649 (SCC) along with it's resistor ladder DAC (051650) allowing for single slot music playback on a MSX computer using Japanese MML compilers such as MGSEL, MuSICA or Performer OPX...

Finally these are pictures of the bottom of the board with the VRC7. The blue board is just a mechanical adapter to allow the connection of a FAKE OPLL (U3567) to a real OPLL connector.

Image

Image

I used a gutted 27512 EPROM "body" as pin carrier for the adapter part as one can notice in the pictures.

Edit 2: I actually fixed the oscillator circuit from the older picture, moved one 27PF and 1Mohm resistors from bottom of the board to the permanent position on top. Resistor is behind the quartz oscillator.

edit: yep... I'm tired of typing the same thing over and over ...


Last edited by l_oliveira on Thu Jul 24, 2014 3:57 pm, edited 1 time in total.

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PostPosted: Thu May 24, 2012 6:57 am 
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I should only note that SSG part of YM2203 and SSG-EG registers of YM2203 and YM2612 are separate things that only share the same name. I.e. YM2203 SSG part has a single envelope generator (just like YM2149F), but it does not interfere with 3*4 SSG-EG generators of the FM part, they could be used simultaneously. I guess the SSG-EG registers were named so just because they function in a similar way.

There were long time doubts that the SSG-EG registers are not function properly or at all in (some) YM2612's or its integrated counterparts, because of the Sega's official docs, but it seems that in fact they are always there and works just like in 2203.


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PostPosted: Thu May 24, 2012 7:02 am 
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80sFREAK wrote:
No, no, this one. Nice! :D Hows YM2203 sounds? I have one, but untested yet(desoldered from sound card looking board).


Make sure you extract the YM3014 chip too (8 pin DIP) or else you will be stuck with SSG only sounds... ;) Edit: My board has the YM3014 assembled under the YM2203 inside the socket middle empty space. Also, there's a address decoder chip under the Intel flashrom. The flashrom has the MSX BASIC driver for OPLL (MSX-MUSIC).

After I'm done playing with the VRC chips I'll play with this little fella on the MSX ...

Image

Image

(This board is tested and produces music correctly if the chip receives commands)

edit: dang Picasa stop breaking my links


Last edited by l_oliveira on Thu Jul 24, 2014 3:59 pm, edited 1 time in total.

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PostPosted: Sat May 26, 2012 6:46 am 
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rainwarrior kindly uploaded a recording from the VRC7 chip operating in a MSX computer in parallel to a real YM2413:


http://dl.dropbox.com/u/883356/VRC7_and_YM2413.ogg


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PostPosted: Tue May 29, 2012 10:34 pm 
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What's the song used? It sounds pretty nifty. :D


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PostPosted: Wed May 30, 2012 4:36 am 
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l_oliveira wrote:
rainwarrior kindly uploaded a recording from the VRC7 chip operating in a MSX computer in parallel to a real YM2413:
http://dl.dropbox.com/u/883356/VRC7_and_YM2413.ogg
Came as rainbow.

Well, now i have more points to use YM2413


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PostPosted: Wed May 30, 2012 7:24 am 
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another sample:

http://wiki.nesdev.com/w/index.php/File ... _MGSEL.ogg

This one is more suitable for compare as it has no reverberation/echo and only melodic output from YM2413 is connected.


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PostPosted: Thu May 31, 2012 8:03 am 
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Almost done with this:

Image


Image
Image


Now to build the RAM backup control circuitry and the audio mixing hardware. ;)

edit: so many broken links ... so little patience ...


Last edited by l_oliveira on Thu Jul 24, 2014 4:04 pm, edited 1 time in total.

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PostPosted: Thu May 31, 2012 11:15 am 
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And finally, the whole point of all this:


Image


http://wiki.nesdev.com/w/index.php/File:VRC7_and_YM2413_on_FAMICOM_LP_intro.ogg


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