So first, maybe it's no surprise that I have created a new NES cartridge board. It is my 6th cart board design. Recently I was asked "better than the last board?", and the answer is no, it's cheaper than the last board. I call it Cheapocabra, or goat-ROM.
Those pictures are of the prototypes, the production version will be a different color and is a revised version, as well. After I make some changes and additions, I'll post the full documentation on it. But here's the basic functionality of the mapper:
- 512kB PRG-FlashROM, in 32kB pages, OR 256kB PRG-FlashROM in 16kB pages, upper or lower 16kB fixed
- 16kB pattern table RAM, in 8kB pages (see errata note)
- 8kB name table RAM, in 4kB pages, 4-screen mode
- 7.5kB bonus PPU-RAM at $3000-$3EFF, in 3.75kB pages
- no bus conflicts, no jumpers to solder, no variants, self-programmable by NES code
- 2 LEDs, 1 red and 1 green, controlled by NES software
- (optional) debug serial output connector
Update, see this post:
This will be my first board that will be factory-assembled, and available to the public. About pricing, I'm interested in supplying it at a reduced rate to independent developers who are interested in self-publishing. I may be able to provide some distribution services, but this may depend on the availability of my time. I am also currently working with a new, small publisher who's doing some high-quality work. I'm open to working with other publishers or distributors, my only requirement is that they have absolutely no involvement with selling bootleg or "repro" carts.
With this board, as well as using it for some software releases of my own, I want to produce an inexpensive devkit, hopefully for no more than $35, that would include this cartridge, an NES-to-USB interface, and software to allow easy uploading and testing without removing the cartridge from your NES.
And secondly, since a cartridge isn't complete without a plastic case to put it in, I've teamed up with a few people to buy our own injection mold tooling. I will have my own cart shells.
I'm expecting the assembled boards to arrive soon, but in the meantime, the cart shells are here. The standard cart shell for Cheapcabra/GTROM is translucent charcoal grey. You can see the green rev2 prototype inside. The production boards will be black. LEDs don't photograph very well, but I took a couple pictures of the LEDs lit up in the cart shell. If you're wondering about the NES, that's my home-made top-loader. And the toggle switch on it is a lockout disable.
Mapper specs were updated to include the "bonus memory" in PPU space at $3000-$3EFF. This can be used as RAM by the CPU, with the limitation that it must be accessed through the PPU I/O port ($2006/$2007).
Added errata note about pattern table paging. The nametable paging is also affected, but there is a software work-around that prevents it.
To clarify about the availability of pictured cart shells, that particular type purple shell will not be for sale. Currently, only the 'Cheapocabra standard' translucent charcoal grey is in stock. The 'traditional' grey shells are not in stock, black shells are in limited stock, but either may be ordered. For $100 flat fee, you may order your own custom color. Pricing for 'non-standard' colors will vary by your lead-time requirements. Minimum lead-time is about 10 weeks. If you want any color besides charcoal grey, please make arrangements as far in advance as possible. If I'm aware of your time-table early enough to combine your custom color with another batch order, then it's possible that even your custom colored shell will cost nothing extra beyond the $100 flat fee. Shorter lead times are going to cost more.
Finally! It took longer than expected, but now the GT-ROM-02 production boards are here. It's had a rough launch, with a board revision before production, and even this version has some quirks that I'm not happy with, but it is still usable.
If this mapper is too basic for you, I have another design in the works with some unique features that I will describe once it's fully tested. I finally bought myself an oscilloscope (Rigol DS1054Z) so I can see what the hell is actually happening.
I've got good news on the sprite DMA glitches, it appears that it was only in my imagination. I mean, it was actually happening, but when I take the cart off of the Game Genie, it doesn't happen. This Game Genie, running my own ROM replacement, is what I'm using to program and test these boards, and I normally just leave it on. Maybe I left it's registers in a bad state somehow. It's a pretty big question mark sitting on the data bus. So it looks like I can put that issue to bed.
In other news, I've been putting these boards through the burn-in test and that's going very well. So far I've only had to touch up solder joints on a few of them. Already, over half of the boards in this batch are spoken for. But there are plenty left over. After I check if it's OK, I'll start naming the first games that will be coming out on this hardware. At least one of them even makes use of the flashROM for save data.
Added link to Cheapocabra Devkit Quick Start Guide
rainwarrior has added support for Cheapocabra (mapper #111) into the FCEUX emulator. Including FlashROM support! Only lacking features are the LEDs and extra PPU RAM at $3000-$3EFF, due to the way the emulator was originally written. I've uploaded a Win32 build of it here:
List of games that have been distributed on GTROM (let me know if I missed any), roughly in order of release:
- Swords and Runes, Sole Goose Productions
- 0-to-X, Sole Goose Productions
- The Incident, KHAN Games
- KHAN Games 4-in-1 Retro Gamepak, KHAN Games
- Sly Dog Studios’ 3-in-1 2P Pak, Sly Dog Studios
- Cowltiz Gamers Adventure
- Scramble, KHAN Games
- Tailgate Party, Orab Games
- Four, by zi (music cart)
- Spook-o'-tron, Sole Goose Productions
- Candelabra: Estoscerro, Sly Dog Studios
- NEScape!, KHAN Games (coming soon)
- ????, Membler Industries (coming eventually)
GTROM mapper for PowerPak, by NovaSquirrel