ApolloBoy Posted March 18, 2007 Share Posted March 18, 2007 If I were to make 7800 homebrews, which sound chip should I use? I'm thinking either a POKEY or a YM2612 (same as in the Sega Genesis)... Quote Link to comment Share on other sites More sharing options...
supercat Posted March 18, 2007 Share Posted March 18, 2007 If I were to make 7800 homebrews, which sound chip should I use? I'm thinking either a POKEY or a YM2612 (same as in the Sega Genesis)... I don't know of any boards laid out for the YM2612. I think it might be intriguing to use a small micro like a CY8C27123 (8-pin DIP, $5 ea or $250 per hundred) as a sound generator but I haven't particularly pursued that. Quote Link to comment Share on other sites More sharing options...
Mord Posted March 18, 2007 Share Posted March 18, 2007 If I were to make 7800 homebrews, which sound chip should I use? I'm thinking either a POKEY or a YM2612 (same as in the Sega Genesis)... Are YM2612's readily available without having to tear apart a genesis to add it to a cart? (Although it would be amusing to see the abject horror on the faces of Sega Genesis fans to see model-1's torn apart for a 7800 game. ) I'd be curious to see a YM2612 in action on the 7800 but I guess it would depend on how much resources it sucks out of the already crunched 6502's processing time. Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted March 18, 2007 Share Posted March 18, 2007 I don't see why it should suck any resources unless you're trying to do PCM audio. The Maria chip, on the other hand, is a bus-sucking vampire. It would be very hard to keep up with PCM with it turned on. The YM2612 plus the TIA sound combination might work out very well, since the FM generator can't do things that an old-school sound generator chip can. The main problem you're going to find is lack of support. No emulator support when developing code (though it shouldn't be too hard to set up in MESS), and no board support. The one plus for board support is that it's not a 40-pin chip, so there's no need for a T-board. And then there's the issue of finding chips that someone mentioned. I have a brain-dead Genesis which I could pull one out of, but that wouldn't do me any good since I've switched to programming the Genesis for non-sound reasons. Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted March 18, 2007 Author Share Posted March 18, 2007 Are YM2612's readily available without having to tear apart a genesis to add it to a cart? (Although it would be amusing to see the abject horror on the faces of Sega Genesis fans to see model-1's torn apart for a 7800 game. ) I'm still not quite sure on that part, as I opened up my model 1 Gen not too long ago and I didn't see a YM2612 anywhere. Mine was made in 1992, so I'm guessing the YM2612 was integrated with the VDP on later models. Quote Link to comment Share on other sites More sharing options...
TailChao Posted March 18, 2007 Share Posted March 18, 2007 Use a YM2151, these are still readily available and heavily documented. The chip package is also nice and small and it doesn't eat up too much address space. Plus, 8 Channels with four operators each is quite excellent. Quote Link to comment Share on other sites More sharing options...
gdement Posted March 19, 2007 Share Posted March 19, 2007 Use a YM2151, these are still readily available and heavily documented. The chip package is also nice and small and it doesn't eat up too much address space. Plus, 8 Channels with four operators each is quite excellent. If I understand correctly, I think the YM2151 requires an external DAC to get analog output. If that's the case then it wouldn't be very practical in a cartridge. The YM2413 however has that integrated, and is also only 18-pins. I have no idea about the availability of them though. YM2413 was used in the Japanese SMS Mark III and is a cost reduced version of the OPL2 Sound Blaster chip (YM3812). The YM3812 would be pretty easy to scavenge from old socketed Sound Blasters, even 2 at a time from SBPro cards. But it also requires an external DAC (again unless I've misunderstood how these things work). Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted March 19, 2007 Author Share Posted March 19, 2007 The YM2413 however has that integrated, and is also only 18-pins. I have no idea about the availability of them though. YM2413 was used in the Japanese SMS Mark III and is a cost reduced version of the OPL2 Sound Blaster chip (YM3812). I thought about using a YM2413, and they seem to be plentiful. I'll have to check it out... Quote Link to comment Share on other sites More sharing options...
Bakasama Posted March 19, 2007 Share Posted March 19, 2007 If I understand correctly, I think the YM2151 requires an external DAC to get analog output. If that's the case then it wouldn't be very practical in a cartridge. It may not be practical in cart form but I suppose it could be done as a pass thru cart or add on board. Quote Link to comment Share on other sites More sharing options...
Richard H. Posted March 19, 2007 Share Posted March 19, 2007 What about the AY-3-8912 ? There's plenty of support / tools for it Quote Link to comment Share on other sites More sharing options...
gdement Posted April 11, 2007 Share Posted April 11, 2007 What about the AY-3-8912 ? There's plenty of support / tools for it From looking at the datasheet, I think it would require an external mixer to combine the 3 channels. It appears to only output the channels on separate pins. I don't know how big a deal that would be though. At least they're analog. Can you mix analog channels by just tying the wires together? Quote Link to comment Share on other sites More sharing options...
PacMan Posted April 11, 2007 Share Posted April 11, 2007 This document have some good information about the chip. Quote Link to comment Share on other sites More sharing options...
gdement Posted April 18, 2007 Share Posted April 18, 2007 Can you mix analog channels by just tying the wires together? I was just looking at an Intellivision schematic, and that's how they mixed the channels. So if anybody else was wondering the answer is yes, the outputs can simply be shorted together. The 40-pin version also appears to be widely available (much moreso than the Pokey), but I'm not sure about the pin reduced versions. Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted April 19, 2007 Share Posted April 19, 2007 Are YM2612's readily available without having to tear apart a genesis to add it to a cart? (Although it would be amusing to see the abject horror on the faces of Sega Genesis fans to see model-1's torn apart for a 7800 game. ) I'm still not quite sure on that part, as I opened up my model 1 Gen not too long ago and I didn't see a YM2612 anywhere. Mine was made in 1992, so I'm guessing the YM2612 was integrated with the VDP on later models. It's a bit late, but here's a pic I had of my own 1601 Genesis: You can clearly see it on the left side. (FYI, the video encoder chip is under the big metal thing at the top left) Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted April 19, 2007 Author Share Posted April 19, 2007 I know where the YM2612 is located on the model 1, but my Genesis doesn't have an actual YM2612 chip. As I said, my model 1 was made in 1992, so it was probably integrated with the VDP like the PSG is. Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted April 19, 2007 Author Share Posted April 19, 2007 BTW, since the YM2612 can do sampling, would the YM2612 be able to use digital samples when used with a 7800? Quote Link to comment Share on other sites More sharing options...
gdement Posted April 20, 2007 Share Posted April 20, 2007 I know where the YM2612 is located on the model 1, but my Genesis doesn't have an actual YM2612 chip. As I said, my model 1 was made in 1992, so it was probably integrated with the VDP like the PSG is. My guess is that it got integrated at the same time they dropped the price to $150 and added licensing protection. If that's the case then most of the Genesis units won't have a discrete YM2612 chip. I think they only sold a few hundred thousand units before the price drop. I'm just guessing about the timing though, maybe the sound chip integration didn't happen at the same time as the price change. Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted April 20, 2007 Share Posted April 20, 2007 My guess is that it got integrated at the same time they dropped the price to $150 and added licensing protection. If that's the case then most of the Genesis units won't have a discrete YM2612 chip. I think they only sold a few hundred thousand units before the price drop. I'm just guessing about the timing though, maybe the sound chip integration didn't happen at the same time as the price change. Nope, my unit in that photo has the TMSS protection, which I found surprising. If you'll notice, on the board there is a silkscreen of two part numbers for the right ASIC (next to VA5/VA6). I suspect the first part number is the pre-TMSS version. I do know there were later 1601 boards because I have one without the holes for the rear port. But this was the same Sega that made like half a dozen different versions of the Saturn motherboard. Quote Link to comment Share on other sites More sharing options...
Gunstar Posted April 22, 2007 Share Posted April 22, 2007 I suggest before any final decision to using something other than the POKEY, that you go to the 8-bit section and see some of the REMARKABLE advances in sound generation tools made in the last few years for the POKEY chip. It's some amazing stuff. If you are not a regular in the 8-bit section just ask about stuff for the POKEY and a bunch of people will show you. Quote Link to comment Share on other sites More sharing options...
gdement Posted April 22, 2007 Share Posted April 22, 2007 Nope, my unit in that photo has the TMSS protection, which I found surprising. If you'll notice, on the board there is a silkscreen of two part numbers for the right ASIC (next to VA5/VA6). I suspect the first part number is the pre-TMSS version. I do know there were later 1601 boards because I have one without the holes for the rear port. But this was the same Sega that made like half a dozen different versions of the Saturn motherboard. You may be right about that other ASIC part number. For what it's worth though, I compared with my non-TMSS 1601 and noticed mine has a different layout, with 2 smaller ASICs in place of the 1 larger one you pointed out. Neither of the part numbers match the ones on that board. The VDP is also a non "A" version. Lots of variety out there apparently. Mine has 2 tantalum capacitors on top and one electrolytic on the back which appear to be hand rework, so I guess the board you photographed must have fixed whatever glitches they were having on the old one. I can say that mine has not been as reliable as other people's experience with the Genesis. -- Salvaging YM2612's from Genesis consoles doesn't sound very economical to me. Personally I wouldn't consider it unless the chips can be found loose. Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted April 24, 2007 Author Share Posted April 24, 2007 I actually have the RMT tracker and I like it a lot. I've actually managed to compose a couple of tracks that I'll be using in my game. Quote Link to comment Share on other sites More sharing options...
Shawn Posted April 24, 2007 Share Posted April 24, 2007 I actually have the RMT tracker and I like it a lot. I've actually managed to compose a couple of tracks that I'll be using in my game. Any programing started on this game? Quote Link to comment Share on other sites More sharing options...
Math You Posted April 24, 2007 Share Posted April 24, 2007 NEC make some sound chips for mobile/cell phones that might work. There's a demo here: http://www.necel.com/mobile_melody/en/index.html http://www.japancorp.net/Article.asp?Art_ID=8535 start at $5 each http://smaf-yamaha.com/tools/nec/tools.htm not sure if this link is any use Matt Quote Link to comment Share on other sites More sharing options...
ApolloBoy Posted April 24, 2007 Author Share Posted April 24, 2007 I actually have the RMT tracker and I like it a lot. I've actually managed to compose a couple of tracks that I'll be using in my game. Any programing started on this game? Unfortunately no. See my thread in the 7800 programming forum and you'll see why. Quote Link to comment Share on other sites More sharing options...
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