nesdev.org

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.

__

I don't think I ever said I did... They are separate the whole time, sorry if my writing implied that I did this.

NROM should be easier to do than TSROM in every way. Indeed, no rewiring is necessary for most types of ROMs. You were also correct in filling up the chips with the data repeated over and over. It should be working. I can only guess that the problem is with the soldering of some pin(s). Have you checked the connections with a multimeter to make sure all contacts are OK?

Since NROM doesn't need rewiring, you could even test the board with the original ROMs, if they're still usable. If they work, you'll know the problem is the EPROMs or how you programmed them, otherwise it's the board.

I have been using the Super Mario Bros ROM to test it. I will double check the connections when I have time tomorrow. I actually made two of these NROM boards for the hell of it, and they both produce the same error (the second one is an NROM-256-04 from an Ice Hockey cart in case that makes a difference, the first one I made is indeed from Super Mario Bros 1)

I am using M27C512

Could you please post complete code of EPROM's.

Sverker wrote:I have been using the Super Mario Bros ROM to test it.

I meant the original chips you desoldered from the board, not the ones you programmed yourself.

Oh, they kind of got destroyed in the process of removing them.

Tokumaru asked the code of the chips, because there's two types of MASK ROM chips on these cartridges:

JEDEC (pinout matches eproms and there's no rewiring requirements)

NON JEDEC (Pinout is defined by the MASK ROM manufacturer and Nintendo took that consideration on board design)


For instance, TSROM boards only have JEDEC compliant pinout in it's DEVELOPER version as it's intended to use EPROMs by design.

l_oliveira wrote:Tokumaru asked the code of the chips

I wasn't me! =)

But yeah, that might be worth checking out.

tokumaru wrote:

l_oliveira wrote:Tokumaru asked the code of the chips

I wasn't me! =)

But yeah, that might be worth checking out.

Ops it was 80sFREAK ! my bad ... O_O

Ah, I don't know, I've been messing with a lot of carts lately and the chips are strewn about my desk and I don't know which came from which board. Any way of telling from the board itself?

Sverker wrote:Ah, I don't know, I've been messing with a lot of carts lately and the chips are strewn about my desk and I don't know which came from which board. Any way of telling from the board itself?

Usually MASK ROMS from Nintendo have the game code in them like for example:

HVC-UM would be the code for the Japanese copy of Super Mario BROS3.

There would be two chips on the cart:

HVC-UM PRG
HVC-UM CHR

There would also be manufacturer code on the chips as well.

I cannot for the life of me find the SMB1 chips, I'm afraid I might have tossed them, but the Ice Hockey ones are: "NES-HY-0 PRG RP23256E 2041 8G3 17" and "NES-HY-0 CHR RP2364E 2021 8G4 32"

After splitting rom put chr and prg files in a folder and create a new txt file. Open new txt file and paste what's in quotes in it.
"copy /b *.chr chr.BIN
copy /b *.prg prg.BIN"
Save file and change extension from *.txt to *.bat.
Now copy and paste chr file till they equal 64 KB and repeat for prg file.
Now run bat file and you should have the right size bin files for 512.
If you've already done all that then if you are using a front load nes you may need to put something on top of cart to hold in correct place since the positioning bar I'm guessing is removed. I've notice some carts work every time but some need this done.