UNROM cart - NESdev BBS

UNROM cart
by tepples on 2006-10-09 (#18311)

I just thought of a way to raise funds for making and selling devcarts: start by selling a (fully assembled) multigame cart with five NROM-128 homebrew games on it. The games would have to be recompiled in $8000-$BFFF, meaning the NMIs and APU IRQs would have to be routed through a JMP in RAM like in Kirby's Adventure and DMC won't be usable, but I think it should work.

Bank 0: Game 1 PRG
Bank 1: Game 2 PRG
Bank 2: Game 3 PRG
Bank 3: Game 4 PRG
Bank 4: Game 5 PRG
Bank 5: Game 1 and 2 CHR
Bank 6: Game 3 and 4 CHR
Bank 7: Game 5 CHR and menu

And for each cart sold, give some money to the developer.

Would this be viable?

by Memblers on 2006-10-09 (#18316)

Yes, it's viable. And it's the direction I'm wanting to go with my Garage Cart series. But I'll come up with some new boards to accomodate more features. Of course we could get a pretty good run from just UNROM though. It's also easy to build it so the $8000-$BFFF page is fixed, and $C000-$FFFF is swappable.

The CHR can be compressed, so that gives more room for a better menu/intro or even another game.

by Bregalad on 2006-10-12 (#18393)

My game, Dragon Skill, will most probably be released by the start of 2007.
If will have 32kb PRG and 32kb CHR (by 8kb chunks) using a CNROM board and vertical mirroring. It won't use DPCM.

It would be cool you'd consider including it, while I don't think you can do anything before the game is terminated and released.

by Quietust on 2006-10-12 (#18395)

Bregalad wrote:
My game, Dragon Skill, will most probably be released by the start of 2007.
If will have 32kb PRG and 32kb CHR (by 8kb chunks) using a CNROM board and vertical mirroring. It won't use DPCM.

It would be cool you'd consider including it, while I don't think you can do anything before the game is terminated and released.

Er, this is fundamentally different from the cartridge specs listed by tepples and Memblers. For one thing, you have 32KB PRG, which doesn't work with UNROM since it would displace the menu. Second of all, you can't change CHR banks with UNROM unless you halt your game and write all of the data in.

by tepples on 2006-10-12 (#18400)

Quietust wrote:
Er, this is fundamentally different from the cartridge specs listed by tepples and Memblers. For one thing, you have 32KB PRG, which doesn't work with UNROM since it would displace the menu.

It wouldn't be hard for Memblers to modify UNROM into BNROM, would it? This wouldn't allow for direct CNROM support, but it would allow for NROM-256.

by Memblers on 2006-10-12 (#18403)

As long as it's not doing mid-frame CHR switching. Solar Wars is also CNROM, and it's on Garage Carts #1 and #2. I simply hacked the CHR bank write into a JSR to a CHR unpack/load routine. GC#1 though uses 32kB banking, and GC#2 probably will also (due to a couple games using DPCM, and me not having immediate access to the source code and not wanting to mess with a disassembler unless I really have to). 16kB or 32kB, not a problem (except for my unfortunate 32kB page design error, that's pretty minor though).

But still, with the source I could probably hack Dragon Skill to run in 2 overlapped 16kB banks if I have to. I'd be willing to do whatever it takes pretty much to get things going.

And vertical mirroring btw is good, so far that's the setup for both carts. There will be an H mirroring cart in the series at some point, because I know one really nice game someone made that needs it. It'll require a special mapper anyways (yet to be designed, and no it's not Grandtheftendo). Especially if I want to carry out my plan of doubling the ROM size for each release in the series, and including all the previous games (would that be cool or what? heheheh).

Only bad thing with that idea is it dilutes the % of royalties for each developer, even if the price jacks up a bit (which I'd rather avoid). Backup plan for that is to do individual game releases also, so fans of a particular game can show their support.

by tepples on 2006-10-12 (#18410)

Memblers wrote:
Especially if I want to carry out my plan of doubling the ROM size for each release in the series, and including all the previous games (would that be cool or what? heheheh).

Only bad thing with that idea is it dilutes the % of royalties for each developer, even if the price jacks up a bit (which I'd rather avoid).

Which is why there aren't any duplicates in Midway Arcade Treasures series. You don't need to carry the old games into the new collection; just keep separate SKUs.

by Bregalad on 2006-10-13 (#18417)

Dragon Skill doesn't use mid-frame CHR switching right now, and I don't think I'll use it later, but I'm not 100% sure, though. Maybe a such thing will be needed on special boss-battles or for the ending or whathever, but chances are rather low.
We'll talk about that after the game will be released I think. You'll be able to have the source as long as you don't distribute it to everyone (because I don't want a thousand of variations/hacks of my game made by everyone).