MMC1,2,3,4/Sunsoft-5B reproduction circuit boards. INL-ROM

[infiniteneslives]

Actually, they used it for 3 square channels in Gimmick!, and ignore the noise and envelope generators. The reasons are sensible, I think. The 2A03 already has noise. The envelope generator as an envelope is kind of made obsolete by volume macros. The envelope generator as bass is okay, though at the given clock rate it's really hard to tune. However, Sunsoft already had a strong tradition of DPCM bassline technology, so it wasn't needed anyway.

The other thing is it's a YM2149F, not an AY-3-8910, and the reason this is important is that the YM2149 has a pin setting that divides the input clock by half (which is how it is used in the Sunsoft 5B), so if you're using an AY-3-8910 you'll need to manually divide the clock if you want the correct pitch.

Thanks for breaking it down for me on the sound technicalities.

Yeah I actually have both a YM2149 and the AY8910 pictured, and tested both. For the AY8910 I'm dividing the clock within the CPLD to keep things proper. I also noticed the YM was significantly quieter than the AY which I brought up here. I should be able to tune it better to make up for the lack of volume but the 8910 will do fine. I had thought about configuring the CPLD so the YM was required since the clock wouldn't have to be divided. But it only saves a single macrocell, and 8910's are much easier to find and thus cheaper as well. I figure I'll just configure it to provide clock division so any chip will work including the smaller 8912. If there are volume issues just pick other values till you find what's best, or use a 10K pot for your audio mod.

[Jarhmander]

Actually, they used it for 3 square channels in Gimmick!, and ignore the noise and envelope generators. The reasons are sensible, I think. The 2A03 already has noise. The envelope generator as an envelope is kind of made obsolete by volume macros. The envelope generator as bass is okay, though at the given clock rate it's really hard to tune. However, Sunsoft already had a strong tradition of DPCM bassline technology, so it wasn't needed anyway.

Actually, even if the 2A03 has a noise channel, I think a second one is still useful for sound effects, so you can use i.e. a thin rattle noise effect without disrupting the drums. In fact, that would make that audio expansion a sensible choice for a game, as AY derivatives was used a lot in older game consoles and proved to be good sounding. I think it is really reasonable to use the 2A03 exclusively for music, and the "AY part" for FXs and music accompaniment.

[rainwarrior]

I was just giving justification for not using it in Gimmick. Gimmick never uses sustained noise in its music, it's all hats and snares basically, and the snares are usually backed by triangle or DPCM anyway, so they still come through partially even when it's interrupted by SFX. I don't personally think any of the YM2149F features are useless, I'm just saying I can see why they ignored them.

On an unrelated note, I was listening to the Black Tiger soundtrack the other day (great use of theme and variations), and apparently it uses an OPN chip, which is essentially a YM2149 + 3 channel 4-op FM. In Black Tiger all the SFX go on the PSG side and all the music is done through FM, so they never conflict. I guess the Genesis has a similar hardware configuration, i.e. several "music channels" and a few PSG "sfx channels", by design. (Though there are many Genesis games that make great use of the PSG for music.)

[infiniteneslives]

The envelope generator as bass is okay, though at the given clock rate it's really hard to tune. However, Sunsoft already had a strong tradition of DPCM bassline technology, so it wasn't needed anyway.

Perhaps a noob question: Out of curiosity would it then be much of an advantage if it could be clocked directly by m2 vice m2/2? Or not really worth the hassle?

[rainwarrior]

It's not a big deal for the squares, but clocking it directly by M2 would get you another octave of usable tuning range for envelope bass. As-is the 5B envelope bass is just barely usable in my opinion, but at the full rate it's directly comparable to the ZX or Atari ST, much more viable.

[mikejmoffitt]

I thought driving it directly with M2 would pitch it an octave up from M2/2, not the other way around.

[rainwarrior]

It does pitch it up an octave. This takes an octave off the bottom of the squares' range, but it also adds an octave to the top of the envelope's range. So, you get an extra octave of usable envelope bass tones. So, it's a trade-off. Do you want an extra octave at the bottom of the squares (M2/2), or do you want an extra octave at the top of the envelope bass (M2)?

Well, calling it an extra octave is maybe not the best description. At the bottom of the range where there's a lot of numerical precision it feels like you're gaining or losing an octave. At the top of the range, you don't really have much precision and the highest few possible pitches increase rapidly (you don't have entire scales available). What you're really gaining is precision, which allows more tunable notes in the high end of the range.

So, if you use M2, the squares have the same range as the VRC6 (can go one octave lower than APU), and the envelope bass has a lot more flexibility. If you use M2/2, the squares can go an octave lower, and envelopes can be very slow (~20 seconds, vs ~10 seconds) but overall pitch precision is halved.

Personally I'd stick with M2/2 for compatibility with Gimmick, but M2 will give you capabilities that are a lot closer to the "classic" AY sounds you'd get from a ZX or Atari ST.

compare:
- Toki on Atari ST http://www.youtube.com/watch?v=UGVy2_rIuLQ#t=3m35s
- translation to Sunsoft 5B: toki_stage_6_on_5b.mp3 (attached)

I made this attempt to translate my favourite Atari ST soundtrack to Sunsoft 5B earlier and discovered just how little envelope bass resolution the 5B has available. As you can hear from this example, the envelope bass just doesn't have the precision to play the notes needed for this tune.

[infiniteneslives]

Personally I'd stick with M2/2 for compatibility with Gimmick, but M2 will give you capabilities that are a lot closer to the "classic" AY sounds you'd get from a ZX or Atari ST.

But what if you could have your cake and eat it too?

My thought was to have a bit in one of the registers control if the mapper was sending the 8910 M2 or M2div2. It could start up and default to a value that gimmick didn't affect keeping it at M2div2. But if a music man wanted to get some better performance because the hardware existed to do so they could. The option could be left out completely and only added in upon request as well I guess.

[qbradq]

I am drooling over this sexy board! Please sell me one! I'd love one configured for stock MMC3 with PRG-ROM, CHR-ROM, SRAM, battery and sockets for the ROM chips as I'll be using it as a dev board. Please advise how long it'll be and what the final cost will be.

This is exactly what the NES dev community has needed for a long time! Thank you so much!!!

Any idea what the ball park would be for a pre-assembled 50 board run with programmed EPROMs? Just curious on how production runs would work for finished games.

[infiniteneslives]

Thanks qbradq, recently I was actually thinking about shooting you an email about this project. I know it was something you had been working on/hoping for well over a year ago when I was first getting into nesdev. Really I have you to thank for the idea and brainstorming of the NESDEV1 project. I've taken a break from that for a bit to work on these boards mostly because of assembly challenges...

I've addressed the costs here in this thread:

I'll be keeping the same prices I posted a few pages back for small quantity/individual sales since everything went as planned. I'll probably have some deal where if you buy so many boards you get one more free as well. If anyone is interested in using them for publishing a homebrew we can negotiate cost, but basically I'd only be looking to charge for labor costs essentially.

For production runs I'd prefer to discuss details in private. I'm willing to do the work to provide fully assembled boards EPROMs and all. There will most certainly be discounted rates for larger orders and homebrew productions. I've already made up a few of these and have some good ideas for the second version that will allow me to assemble them with a lot less time and effort so that should be a win win as well.

Right now the only thing I'm waiting on is Jim's Cool open CIC to be finished up. He's made good progress recently and I expect the CIC's will be verified and available soon. I've worked out all the kinks on my MMC3 design for these boards so I could sell them now especially for homebrew development needs. I've yet to put the formal documentation together which I'd like to do for the formal release.

Additionally I did pick up a fair quantity of PLCC sockets for the CPLDs. I thought they might be of interest to deving with the boards. One could buy several mappers and one fully socketed board and just swap out the mapper chips as desired. I've also got several other mappers in the works so 'upgrading' would be easy. One could even try thier hand at creating your own mapper if one had a jtag programmer, I can recommend a ~$30 one I picked up recently.

[qbradq]

That's funny, your work on this and NESDEV1 are the reasons I came back to NES dev Looking forward to using this sexy, sexy board!

[qbradq]

I forgot to ask this. I got confused over the six page read. Will my memory chips need to be 3.3v tolerant on the signal levels or not?

Thanks!

[infiniteneslives]

I forgot to ask this. I got confused over the six page read. Will my memory chips need to be 3.3v tolerant on the signal levels or not?

Thanks!

Yeah basically the Vih of your memory needs to be below the Voh of the cpld. The data sheet says 2.4v with 4ma load. It's above 3.0v from what i remember under normal address line loading. All the data sheets say 2.0-2.2v for Vih on memory.

Effectively i doubt you could find a 5v memory that isn't compatible... It'd have to be a pretty bum chip to not sense 3v as a logic 1.

[MottZilla]

So when the CIC is finished you'll begin taking orders for boards? Any idea when the CIC will be done, like an educated guess?

[infiniteneslives]

So when the CIC is finished you'll begin taking orders for boards? Any idea when the CIC will be done, like an educated guess?

You'd really have to ask Jim's cool about that. For what its worth I would like to see my boards for sale in a month or less.