Making SEGA Genesis cartridges

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bulldawg:
Removing the two chips worked, did not have to add jumpers. Thanks

pbj:
So, I took a deeper look at Quarterback Club 96 vs Mortal Kombat Arcade Edition. I had no idea that there was a single chip 4MB ROM game with saving, and that could actually be a useful PCB for Phantasy Star 4, Beyond Oasis, and some of the new homebrew like Cave Story. I don't think I've had one of those PCBs come across my desk, but I'll definitely take a closer look.

Anyway, here's how the two headers compare:

Notice that the ROM End address is total nonsense on MK, instead of RA it's got ||, and 5421 instead of E840. It also points to a non-standard SRAM start and end address. I've contacted the patch creator about some of his other SRAM patches, most recently his Ghostbusters one, and he and I have a difference of opinion on what "tested on actual hardware" means. He's playing these on Everdrives, and the layer of emulation those have ignore these mistakes and work anyway, but none of this will work on an actual cartridge. Even going in and manually correcting this won't make it work, so in short I have never gotten a single one of his SRAM patches to work on actual cartridges. (and I've tried many of them) He did release a revision of Ghostbusters that fixes some of the header junk. Still doesn't save on a real cartridge.

:cheers:

bulldawg:
Fyi College Slam is the same way.

pbj:
Well, all those 4MB Akklaim boards are also ones where you can just simply pry off the ROM, so I actually had about a dozen of them stripped and ready to go.

I gave it a couple of tests with Cave Story. Once with no modification to the header, and a second attempt where the header had been modified to match Big Hurt on the SRAM start and end spaces.

Anyway, booted fine with both setups but would not save on either. I like Cave Story as a test because it's fairly tolerant and you know within moments if saving will work or not. So unless the game is programmed to use EEPROM, I'm doubtful it's going to work.

I've attached the document from the Everdrive website that discusses all the different EEPROMs. Really the only thing of interest is that Sports Talk Baseball can be directly converted to Wonder Boy in Monster World.

(and College Slam is actually a decent game)

pbj:
I really need to clean up the first post on this thread and edit it to have all the useful information.

Anyway, this is mostly for my self reference, but here's how to use those old SEGA boards with the chips popped off. This time with cleaner jumper wires. The only thing happening on the back is I've cut the line from pin 42 of the EPROM to 5V. Pac-Mania is a tiny ROM, so I'm pulling the 2MB pin to ground (wouldn't boot otherwise...). Punisher and Robert Cop 2 are both 2MB, so I jump that pin to a trace running to the 2MB pin on the cartridge connector.

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