Here's a post I did a long time ago on one of the other forums. Scroll down to the part when I mention NROM.

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I'll give some general tips for repros in general, and then a detailed description for Recca.

General tips:
Launch the ROM in Nintendulator. There should be a Debug Information window. In that window you should see info telling you things like: Mapper type (Recca is mapper 4 or MMC3), size of PRG (Recca is 128), size of CHR (Recca is 128) and the type of mirroring (Recca is horizontal). If there is extended header information you should also note that as well (supports battery backup, etc..)

Note on mirroring. You do not need to find a donor cart that matches for mirroring, you can switch it. Example: To switch a cart from horizontal mirroring to vertical mirroring, you'll need to desolder the pad on V and solder it to H. (Yes, it's backward. Think of the letter representing the scrolling)
Mirroring does not matter when getting donors for MMC1 and MMC3 since it is done by the software. (ie: you dont switch anything for Recca)

Now that you know which type of donor cart you need, go to this page
http://www.parodius.com/~veilleux/boardtable.txt
This is useful for NROM, CNROM, UNROM donors, but not that great for other types.
Kevtris has a good list of MMC1 details:
http://www.tripoint.org/kevtris/mappers/mmc1/index.html
Recca is MMC3 and you will want a TSROM donor.

So use the boardtable and get an TSROM. Take it apart, de-solder the PRG and CHR chips. Get another one and try again (because if its your first time de-sodering, I guarantee you'll ruin it. desoldering is tough)


Next thing you need to do is get the proper chips to put on it. RECCA has needs 128 KB chips. EPROMs are in Kb (lower case b) si figure that out by multiplying KB by 8 (128*8 = 1024). Order youself a couple 27C010-150 EPROMs or 29F010 Flash.

You then need to strip the header off the ROM, split it into its PRG and CHR segments. I'm sure there are tools or emulators that will do this for you. I just wrote my own. I imagine some people use a hex editor

In theory you can program the CHR onto a chip and the PRG onto a chip and solder those to the board. In reality you can't, there's more to it.

The chips arent always compatable with the donor without re-wiring them. UNROM donors sometimes dont have enough holes in the donor board for a 32 pin chip.
DRK on nesworld made up a nice doc on conversions:
http://www.nesdev.com/NES%20EPROM%20Conversions.txt

One other thing. If you are putting data on a chip, you must fill the chip.
Lets say you are doing an NROM which has 16K PRG, you ae probably putting it on a 27C256 EPROM (or 29F256 flash) which is 32KB in size. You need to double up your binary file before writing it to the chip. You can do this in DOS by using the DOS copy command.
Example concatenate a file called “theFile” twice (essentially doubling its size) and have its destination be “theDestFile”

copy /b theFile + /b theFile /b theDestFile

NROM is the easiest to start with. There's no re-wiring to do.

I highly suggest you make a dev board first using sockets. If you need to re-wire, re-wire the sockets (not the chips you put in the sockets). A dev board allows you to see if you have prepared/programmed the EPROMs correctly.

I'm no expert, I've only ever done simple stuff. My EPROM programmer doesnt work with chips larger than 128 KB.
EPROMS are cheaper than flash. Flash are easier to use (no need to buy a UV eraser). I've never used One-time-programmable chips, but I believe they are the cheapest (and you can only program them once).

I'm sure I'm missing a ton of stuff. Hopefuly this will help but you should definitely check out www.nesdev.com

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Al

Al,

Thanks for all of this info. I really appreciate this.

I will read it all over thoroughly and then post.

Thank you very much.

T

I've ordered my Willem USB programmer and a super mario bro's cart.

Trying out HXD hex editor, (also looked at translhexion). I like HXD better for some reason, even though I have no idea how to use it yet.

What I don't yet understand is how to physically extract the PRG portion of the hex code and strip off the iNES header.

I can post the hex code of my compiled rom here, tonight.

Thanks again,
T

coinheaven wrote on 15. Feb 2008 at 15:55:

If you have written an NROM game, it will definitely work on a power pak exactly the same as on a real cart (for testing purposes).


As for how to strip PRG, etc...  ALl of that info is located in the header.
The header tells you how many 8KB CHR segments there are and how many 16KB segments there are.  I think the CHR segments are stored sequentially first.  So if you header had 1 for CHR and 2 for PRG, you would strip off the first 16 bytes, store the next 8K as CHR, store the next 2x16=32KB of PRG, and ignore the rest (sometimes people store addiitonal junk a tthe end of their roms).

I'm pretty sure the windows software available for copyNES  (www.retrousb.com) ; has some simple utiltity functions built in.  Even if you dont have a copynes I think you can still use the tools if you put your ROM in the ROMS directory for the tool after you install it (and can then invoke split on the rom).

Al


Al