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Last updated on Oct-18-2019 Download

MMC3 chr-swapping working in emu, not Powerpak

MMC3 chr-swapping working in emu, not Powerpak
by on (#143540)
I am not sure what I'm doing wrong. I'm just doing some simple CHR-ROM swapping and it works fine in FCEUX for example. But a tester confirmed it doesn't work running on PowerPak (=wrong gfx).

I am no expert in MMC3, whatsoever, but here's my code (see below). See anything obvious? Thanks in advance.
Code:
      ldy #%00000000
      sty $8000
      sta $8001
      clc
      adc #2
      ldy #%00000001
      sty $8000
      sta $8001
Re: MMC3 chr-swapping working in emu, not Powerpak
by on (#143542)
I have FCEUX, a PowerPak, and time to help you work through this. First, have you tried creating a small ROM that exhibits the same problem and that you're willing to upload?
Re: MMC3 chr-swapping working in emu, not Powerpak
by on (#143543)
No I haven't done any other test-ROMs at the moment.
I'm working on patching VS Gradius (mapper 151) to standard NES (mapper 4), and here's a work-in-progress (.ips)release.
https://dl.dropboxusercontent.com/u/259 ... tch%5D.zip

(Coins are inserted by pressing Start).
Re: MMC3 chr-swapping working in emu, not Powerpak
by on (#143554)
You need to write ALL of the CHR registers at some point to get them initialized. (This goes for all of the mapper registers! You also need to write the mirroring at $A000, etc.) Emulators are very bad for testing mapper stuff because they'll often boot up in a "friendly" NROM-compatible configurations (maybe to support some ROMs that are using wrong mapper numbers).
Re: MMC3 chr-swapping working in emu, not Powerpak
by on (#143647)
Thanks, you were probably right, I wasn't doing a proper initialization. :)
Re: MMC3 chr-swapping working in emu, not Powerpak
by on (#183838)
I tried your VS Gradius hack in my EverDrive and saw glitched tiles for the first level boss and the volcanic rocks that spew out really fast just before it.