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PostPosted: Mon Apr 09, 2012 7:27 pm 
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So the good news is I recreated the MMC3 on my CPLD with the NESDEV1 cart I'm working on. But ever since Bregalad's chart in the discussion where Tepples created the mapper wizard I've been thinking. Seeing that the community's solution to getting a scanline counter, and CHR-RAM (edit: and WRAM) was to hack up a hard to obtain Japanese cart was hard to swallow. Something as basic as these things shouldn't be difficult to get together. I'm thinking that there is a sizable need or use for a MMC3 reproduction cart similar to retrozone's repropaks but in MMC3 flavor.

Really now that I've proven to myself that I can make them and have a solid design, I'm looking to see what people think of the idea. I don't know of many MMC3 homebrew projects right now aside from miau's Super Bat Puncher. But if something like this were available maybe other people would use the MMC3 in their projects.

The secondary goal would be to give people another option besides hacking donor carts for reproductions. If there was enough demand I'd work on cases and CIC's in the future as well, but for now you'd have to head over to retrozone. His prices are pretty decent though, so I wouldn't see that as much of an issue aside from shipping.

In a basic version it would just be set up to accept different configuratons via jumpers. Like CHR RAM or ROM, TLSROM style 4 screen, larger WRAM etc... Also for the fami guys, depending on what the demand was I would make 60 pin versions of the boards as well.

The other thought kinda stems back to the original idea of the NESDEV1. I kinda went beyond the scope of what the project originally was intended for, but the tool I have now is really what I needed to easily develop these types of things. The CPLD I'm looking at right now should only have half of it's resources used for a stock MMC3. So if there was interest for a more better hybrid MMC3 it could also be implemented on the same board. Maybe try out Tepples' idea of checking CHR A13 for the scanline counter vice the cumbersome CHR A12 clocking. My other thoughts were perhaps Tengen's RAMBO-1 style counter that could be swapped over to a CPU cycle counter. Changes to bank switching and stuff should be within reason also. If something like this were to happen the mapper design would be published. That way the mapper's hardware details would be known by all.

I know there is other work going on with Member's 8T-ROM with it's MMC2/4 ish behavior and such. And we've got some dev/flash carts also in the mix. But there has been enough discussion of about when a MMC3 board is made available I thought I'd offer up the service and see what you guys think. My goal would be to have it for $10 or less, and offer pricing breaks for larger quantities and such. I'm not trying to strike it rich or anything, I just enjoy this stuff and would like to make these available.


Last edited by infiniteneslives on Fri Feb 15, 2013 1:40 am, edited 4 times in total.

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PostPosted: Mon Apr 09, 2012 8:15 pm 
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I think someone should offer a MMC3 clone board to help discourage destruction of old games. People will certainly make reproductions, it might as well be done with NEW parts rather than destroying old games. After seeing some thread where someone was thinking about sacrificing Mega Man 2 that really bothered me. Mega Man 2 was an excellent game, why would you destroy it.

So if you can make up clone MMC3 boards that are functionally the same I think you should.


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PostPosted: Mon Apr 09, 2012 10:26 pm 
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I would consider using the MMC3 in my projects if there was a reliable source of boards. Not that I'm sure I'll be releasing any game physically anytime soon, but it would be nice to know this is a possibility.


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PostPosted: Mon Apr 09, 2012 10:33 pm 
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I had actually thought about this a while ago. I'm for this, especially if a Famicom version could also be produced. Translated carts for the win!


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PostPosted: Tue Apr 10, 2012 1:26 am 
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Okay well I'll start looking into more of the details of what's possible as far as manufacturing and end price goes. I'm guessing there isn't much market for it if I can't keep the price close to $10. It might end up being a pretty large investment for me to get it to that price off the start. If I'm having troubles it might end up that you'll have to buy 3-10 of them to get that price or it would end up closer to $15 in individual quantities.

Part of the biggest issue is there isn't much for 5V tolerant CPLDs that can fit a full fledged MMC3. Most cost effective option is 3.3V parts, but they then require supporting circuitry of level shifters and such which further complicates assembly. Chance are the ROMs used will end up being required to accept 3.3v logic signals, but that shouldn't have much effect.

If the only interest was for homebrew productions it's possible that the MMC3 could be minimized to fit on a cheap 5V tolerant part that would make less than $10 PCB and mapper without a problem. But people prefer different things. One solution would be to restrict CHR memory to 32KB (for CHR RAM presumably). Doing that would reduce the required logic almost by half. In that case it would easily fit in a 5V tolerant CPLD and $8-10 end cost would be simple and I could assemble them myself with the coarser pinned CPLDs. Something like this would be much more achievable for me to produce, but it ends up being our own mapper with MMC3 qualities.


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PostPosted: Tue Apr 10, 2012 3:28 am 
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How's big this market and how much peole ready to pay. Let's figure out price for 10 IC's, 50 and 100


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PostPosted: Tue Apr 10, 2012 4:43 am 
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infiniteneslives wrote:
I'm thinking that there is a sizable need or use for a MMC3 reproduction cart similar to retrozone's repropaks but in MMC3 flavor.

I asked bunnyboy and as far as I can remember, he said he's likely to start selling MMC3 ReproPaks once someone asks in good faith. "Good faith" in this case would mean that someone has finished a homebrew game that absolutely needs a scanline counter.

Quote:
I don't know of many MMC3 homebrew projects right now aside from miau's Super Bat Puncher.

And even that uses an MMC1, not an MMC3. The compo version uses SNROM, the same board as Metroid.

Quote:
But there has been enough discussion of about when a MMC3 board is made available I thought I'd offer up the service and see what you guys think. My goal would be to have it for $10 or less, and offer pricing breaks for larger quantities and such.

I support this, even though I myself don't have an MMC3 game made.


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PostPosted: Tue Apr 10, 2012 9:04 am 
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You should at least design them, just so there are more sources of materials. You would sell a few to developers here, but don't expect to sell much more other than for one or two repros that need specific boards. All other repro makers will still use the much cheaper donor carts.

I have had MMC3/VRC2/VRC4/etc boards available for homebrew production for a while, but I don't expect them to be used by anyone in the next few years. They cost me ~$12 with no profit, while an enhanced UNROM is under $3. Going from a $30 homebrew to $40 would be a large hit to sales so it will need a very good (and actually finished) game to justify the added cost.


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PostPosted: Tue Apr 10, 2012 9:59 am 
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Thanks for the info bunnyboy, I guess we were all wondering about that.


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PostPosted: Tue Apr 10, 2012 11:02 am 
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What is an enhanced UNROM?


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PostPosted: Tue Apr 10, 2012 12:39 pm 
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512KB PRG (Battle Kid 2), self flashable (not yet used), and 4x 8KB CHR RAM banks (Assimilate) are very cheap additions to UNROM. Like the 8T-ROM using flash instead of battery backed WRAM removes much of the need for MMC1/MMC3. The CHR banking makes background animations usually done with CHR ROM easy. Still no IRQ but $5-10 cheaper per cart.


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PostPosted: Tue Apr 10, 2012 1:25 pm 
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Thanks for that insight bunnyboy, you're confirming most my thoughts. Which is good since you've probably got the best pulse on what the market is for these.


After making my comment about a minimalized MMC3 to fit the logic into a 5V tolerant CPLD I got an idea... The issue is it's ~100 macro cells for the full MMC3. And the best priced CPLDs are somthing like the xilinx9500 family but only upto 72 mcell. If you step up to 144Mcells on the 5v tolerant device it starts to become more cost effective to switch over to level shifting on a non-5V tolerant part.

But... the MMC3 could easily be split into two separte smaller CPLDs. Bankswitching in one and scanline counter in the other. That would be around the same price as the larger non-5v tolerant devices but not require any level shifting. The other benefit is that there are more IO and Mcells available, even though you do lose some by doubling some items up. With that there would be room for improved MMC3 designs on the same board. Just flash the CPLDs differently and configure jumpers differently. Additionally they are easier to assemble with coarser pins, which makes it more reasonable for me to assemble the first batch myself, without pulling my hair out.

As for quantities I'd have to make up at least 50 in the first run. PCBs are far too expensive below that. I'm still waiting to hear back on what kind of price break I can get on the CPLDs, but I should still be able to do $12 for the PCB and CPLDs soldered on with a regulator. If I stepped up to making 100 I should be able to meet the $10 mark. Keep in mind this doesn't cover any memory, CIC, or case.


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PostPosted: Tue Apr 10, 2012 6:26 pm 
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If using two CPLDs is cost effective that certainly shouldn't be ignored. I think to get both the homebrew base covered as well as the bit more shadey reproduction base you'd want to make a MMC3 compatible if not straight clone. Because if it is compatible with all existing MMC3 software that ensures a market will exist and you won't end up stuck with unsold units.

Particularly if the board can by like the RetroZone boards where the one board can be configured for various standards of the TxROM.

bunnyboy wrote:
512KB PRG (Battle Kid 2), self flashable (not yet used), and 4x 8KB CHR RAM banks (Assimilate) are very cheap additions to UNROM. Like the 8T-ROM using flash instead of battery backed WRAM removes much of the need for MMC1/MMC3. The CHR banking makes background animations usually done with CHR ROM easy. Still no IRQ but $5-10 cheaper per cart.


With the 32K CHR-RAM, is it just hooking up the upper bits to hold a 8KB CHR-RAM page I would guess?

Part of the reason to have a MMC3 for homebrew is definitely to have alot of CHR, which no homebrew yet has needed but certainly could happen. Alot of great games have such nice graphics thanks to tons of CHRROM.


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PostPosted: Tue Apr 10, 2012 6:59 pm 
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MottZilla wrote:
With the 32K CHR-RAM, is it just hooking up the upper bits to hold a 8KB CHR-RAM page I would guess?

You could still use the regular MMC3 CHR switching scheme (i.e. 4 1KB chunks + 2 2KB chunks), but restricted to those 32KB of CHR-RAM. This would be really useful for character and background animation, pretty much in the same way as CHR-ROM is.

Quote:
Part of the reason to havea MMC3 for honebrew is definitely to have alot of CHR, which no homebrew yet has needed but certainly could happen. Alot of great games have such nice graphics thanks to tons of CHRROM.

Yeah, giving up CHR-ROM is not such a great idea, since that would certainly exclude the repro folks. For us developers though, the 32KB of CHR-RAM is almost as good, the only advantage being that the graphics will occupy space in the PRG-ROM, which has the fairly low limit of 512KB.


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PostPosted: Tue Apr 10, 2012 7:02 pm 
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You could always add a counter logic chip to extend it to a 1MB+ chip on writes that would be very cheap but allow a lot more space over all.


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