Discussion about software development for the old-school Gameboys, ranging from the "Gray brick" to Gameboy Color
(Launched in 2008)
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In order for my game to contain everything I wanted in it, it turns out I will need to step up to a 64KB ROM file which means my 32KB flashcart will no longer do the job and I need to look into a larger cartridge.
I'm going to try to stick with a cartridge designed by me so that I have a bit more control over quality while keeping the cost down as I do plan to make a limited run of this game to sell at conventions. I wanted to see if anyone has designed an MBC1 clone chip, and what chips it would require, so that I can design a larger flashcart and possibly order a prototype run before the end of the year. I am not looking for a flashcart design that requires removing chips from existing Game Boy cartridges, I am trying to build a cartridge from all new parts.
I would also like to keep these as simple as possible as I am likely going to have to solder these myself and don't look forward to soldering 5+ surface mount resistors and capacitors along with 2 chips.
I've attempted to look into MBC1 clone searches, but everything I can find is MBC3/MBC5 or is talking about reusing an MBC1 from a cartridge instead of making new ones.
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What I have found so far was inside Gadgets had a series of posts about making an MBC1/5 hybrid using a EPM3032ATI44-10N CPLD, however that is discontinued and I'll likely have to pay more to get them now. It also runs at 3.3V, meaning I'll have to add an LDO if I go that route, pushing the cost up further. As far as I can tell, the specs I need to focus on for picking a new CPLD are:
-Maximum I/Os (32 on this one, but I'm pretty sure an MBC1 cartridge won't even use half of them as that is more pins than an MBC1 has in total.)
-Operating voltage (3.3 on this one, but I'm going to see if I can source a CPLD that uses 5V so I don't need to add extra parts to my schematic.)
-Maximum operating frequency (pretty sure it won't be an issue.)
-Maximum propagation delay (4.5s is what that chip has, guessing that's what I should aim for.)
I should note that I'm focusing my search on chips where I am able to find an ECAD model so I can use them in EAGLE more easily with a preference for fewer pins as I'll probably have to solder my prototype batch by hand since the PCB manufacturer I was looking at doesn't do assembly on thinner boards like what a cartridge would use.
Chips I'm looking at so far:
ATF750CL-15XU: Primary concerns are if it has enough I/Os and that the package might be too thick to fit under a shell.
ATF1502ASL-25AU44: Cheaper than the ATF750 and has more I/Os
I was looking at an SPLD, but I don't know if these are sufficient for MBC1 functions or not. ATF16V8CZ-15PU was the one I was looking at.
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Why do you want specifically an MBC1 clone? MBC5 is superior in every way, even if you don't use all functionality it has to offer.
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I guess I don't have much of a need for MBC1 specifically, just preference because I guessed it would be easier to implement, would not require as powerful of a CPLD or put less drain on the Game Boy's battery.
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