I took an old SMB1 cartridge and replaced the ROMs with a set of sockets in order to test fresh EPROMs before committing them permanently to another board. I have had luck doing this with a TSROM board (for playing around with Mario Bros 3 hacks) but I have run into some problems with my NROM board.
Let me preface this by saying that, as I understand it, no rewiring is necessary for NROM boards. If I am wrong feel free to tell me how wrong I am.
I decided to test this board by burning the original game (unmodified SMB) to a pair of EPROMs (M27C512) to see what happens. I split the ROM file using CopyNES and burned the respective PRG and CHR data to their own EPROMs, as I have done in the past, using a GQ-4X True USB Universal Programmer. Blank check and write check both passed. I seated the EPROMs in their sockets, loaded the game in, and only got a grey screen with the power cycling every second or so.
I read somewhere on this forum that sometimes when you use EPROMs with a larger storage capacity than the originals, you need to fill the whole EPROM with the same data repeating. As I am using M27C512, double the size of the Super Mario Bros PRG alone, I tested this theory. Using a hex editor I made a pair of new files which contained the PRG and CHR data repeated to fill 512kbits. I burned these to EPROMs, loaded them into the board, and the result was just got a solid grey screen with no looped power cycling. A bit different, but still no dice.
Does anyone with experience hacking NROM boards know what might be causing this? Am I using the wrong EPROMs, or is something else screwing this up?
Thanks for your time.
Let me preface this by saying that, as I understand it, no rewiring is necessary for NROM boards. If I am wrong feel free to tell me how wrong I am.
I decided to test this board by burning the original game (unmodified SMB) to a pair of EPROMs (M27C512) to see what happens. I split the ROM file using CopyNES and burned the respective PRG and CHR data to their own EPROMs, as I have done in the past, using a GQ-4X True USB Universal Programmer. Blank check and write check both passed. I seated the EPROMs in their sockets, loaded the game in, and only got a grey screen with the power cycling every second or so.
I read somewhere on this forum that sometimes when you use EPROMs with a larger storage capacity than the originals, you need to fill the whole EPROM with the same data repeating. As I am using M27C512, double the size of the Super Mario Bros PRG alone, I tested this theory. Using a hex editor I made a pair of new files which contained the PRG and CHR data repeated to fill 512kbits. I burned these to EPROMs, loaded them into the board, and the result was just got a solid grey screen with no looped power cycling. A bit different, but still no dice.
Does anyone with experience hacking NROM boards know what might be causing this? Am I using the wrong EPROMs, or is something else screwing this up?
Thanks for your time.