Hi guys,
I'm just getting into the SNES Repro scene and have a question about SRAM. As there are 2 sizes (64k and 256k) I was wondering, as there is no real price difference between the 2 chips can I just use a 256k on every board or does it have to be specific to the ROM I'm using?
Does SNES SRAM size matter?
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1. NO BLATANT PIRACY. This includes reproducing homebrew less than 10 years old, with the exception of free software.
2. No advertising your reproductions, with the exception of free software.
3. Be nice. See RFC 1855 if you aren't sure what this means.
Re: SNES SRAM Question
You can use a 256 kbit RAM everywhere except for a few obscure Japanese games like Dezaemon, which require a bigger RAM.
But the number of address lines actually connected to the RAM is specific to the ROM because some ROMs do a self-test and halt if the RAM size isn't exactly as expected. To use these ROMs, connect the SRAM's A14 and A13 inputs to ground (and disconnect them from the address lines on the cart edge) so that only the first 8192 bytes (64 kbits) are usable. Furthermore, to use ROMs that expect a 16 kbit RAM, also ground A12 and A11. (If it makes routing easier, you could connect these address pins to power or another address pin instead of ground.)
The other way is to patch the game to skip the self-test, but that's not always easy. Some ROMs, such as Earthbound, have redundant code strewn about to verify the self-test in some manner.
But the number of address lines actually connected to the RAM is specific to the ROM because some ROMs do a self-test and halt if the RAM size isn't exactly as expected. To use these ROMs, connect the SRAM's A14 and A13 inputs to ground (and disconnect them from the address lines on the cart edge) so that only the first 8192 bytes (64 kbits) are usable. Furthermore, to use ROMs that expect a 16 kbit RAM, also ground A12 and A11. (If it makes routing easier, you could connect these address pins to power or another address pin instead of ground.)
The other way is to patch the game to skip the self-test, but that's not always easy. Some ROMs, such as Earthbound, have redundant code strewn about to verify the self-test in some manner.
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Re: Does SNES SRAM size matter?
Excellent, thanks very much!!
Re: Does SNES SRAM size matter?
Hi there,
Long time lurker, first time poster. Sorry to necro this particular thread, but I wanted to ask if the same instructions are true of using 256 chips for NES carts?
Long time lurker, first time poster. Sorry to necro this particular thread, but I wanted to ask if the same instructions are true of using 256 chips for NES carts?