A question about EPROM programming

I've been looking around at different flash carts to develop my own GBA games on (I eventually settled on a EZ-Flash IV) and while looking around, I came across this post: http://callanbrown.com/index.php/basic-nes-reproduction

I'm no electronics expert, but from what I can tell from the post, they remove the ROM chips on the NES game board and replace them with their own programmed EPROM chips.

My question is does this process work with GBA cartridges? Could you just take the ROM chip out of the GBA cartridge and replace it with your own flashed EPROM and it will work? Or does it not really work that way?

Sorry if it sounds like a stupid question

 

Not quite. GBA has a multiplexed address and data bus, so the ROMs contain a little proprietary logic that must be implemented separately--a register to hold the upper address, internal address decoding, and a loadable counter to perform burst access.

Also it's important to differentiate between flash and EPROM. 3.3 V parallel x16 NOR flash is most appropriate for GBA.

 

Not quite. The "ROM" chip might not be just a ROM and will use a different voltage than an NES EPROM. I've seen bootlegs that use off the shelf parts and you can replace the rom with your own flash in those.

 

So you're saying that if I replaced the ROM chip in a bootlegged GBA cartridge with my own flashed EPROM it will play the game that's flashed to my EPROM?

Sorry if what I'm saying makes no sense I'm new to all this

 

EPROM isn't flash. Flash is a type of EEPROM but they're different physical products built on different technologies. Again, it's important to differentiate between flash and EPROM.

If you reprogrammed a bootleg's flash with your own data, you'd be set because the bootleg will implement the necessary GBA bus logic somewhere separately from the flash.

You could however run into complications if the bootleg's PCB layout doesn't match the standard flash pinout. Sometimes products do this to improve routing, or as a basic form of copy deterrence. In this case you'd need to rearrange the data (via software) before programming so that it aligned correctly with the PCB's wiring.

 

Would reprogramming a bootleg's flash be as simple as using a GBA linker cable and writing a rom to it? I doubt it though because if that were possible people would be buying cheap pirated pokemon games and using them as flash carts.

I suppose you could attempt to remove the bootleg's flash, wipe the data (if that's possible) and program it yourself (not sure how you would do that) then resolder the flash back to the board.

How could you remedy this problem? And ultimately, is it worth going through all this trouble (and money) to essentially make a flash cart, when you could just buy a real flash cart online?

 

It depends, and you're right; most likely the bootlegs don't have the /WR (write strobe) signal connected, so you might have to wire that, and GBA linkers will only support programming specific flash ROMs; if the bootleg uses another family of flash, it might not even attempt to program it.

Exactly. You'd need a hot air station, modern universal programmer and some type of TSOP adapter.

You'd have to determine the flash's address and data bus pinout in relation to the GBA connector, then find or write software to rearrange the data (swapping around addresses and data bits).

Of course not, just buy a flash cart.

 

A bootleg won't take an EPROM but it may take a flash chip. Most I've seen that don't use an epoxy blob use a standard part.

If you're going to make more than 1-2 get your own carts made or buy them from someone else who has. It will be cheaper and easier than buying buckets of bootlegs and opening them to see if what's inside is useable.

 

Thank you all for your replies. I learned a lot