Tutorial: Mapper compatibility fix

[Redherring32]

In this very simple tutorial I'll show you how to make your rom work in any emulator/device.

First off you'll need the iNES Header Checker

1. Open the tool.

2. Open your rom.

3 set the drop down to say "2-UnRom PRG 16k swap".

4 Click save (it won't seem like it did anything but it saved).

Done, now your rom will work in any emulator/device you want!

 

[Kasumi]

2 caveats:
Some emulators (Maybe just puNES?) only accept historically existing sizes for mapper 2. (NES Maker games are always 512KB, 256KB is as large as UXROM games got as far as commercial releases to my knowledge.)
If NES Maker adds CHR bank switching, it is likely to make this stop working. (Your game will crash because the bits used for CHR swapping would get interpreted as PRG banks). Edit: Actually.... maybe not, now that I think more about. Since the CHR bits are higher, you might just always get a mirror of the PRG bank you want! That makes the only potential failure the single screen mirroring bit.

Edit: I wrote this post a bit ago that describes how to do it for the NES Maker user and goes into a bit more detail and what's really happening: http://nesmakers.com/viewtopic.php?f=23&t=674&p=5969&hilit=punes#p5969

Shorter: It'll work most of the time, but it's not a magic solution.

 

[Mihoshi20]

I've actually toyed with this a bit myself though to a more critical degree when adapting and testing my game on MAME's implementation of the Vs. System and Playchoice-10 hardware. Though the implementation in MAME is very picky about UNROM specs and since anything over 128KB would be absolutely rejected by the emulator, i had to do a bit of trimming and bank rearranging to make my game fit the parameters. Which makes me hope that 4.1.0's engine has replaced all hard coded values with their proper constants.

Rereading though that post you made Kasumi, it's amazing we were talking about 4.1.0 as far back as September. Still a lot of good info there I'll still be using to convert my games for UNROM testing until the feature is implemented into NESmaker officially.

 

[dale_coop]

Yeah, it would be great to have a real solution to produce mapper 2 roms directly out from NESMaker.
I use "iNES Header Checker" sometimes (when the emulator I use doesn't support the mapper 30), but I would prefer something more clean.