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PostPosted: Sun Mar 22, 2015 12:14 pm 
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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

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PostPosted: Sun Mar 22, 2015 12:34 pm 
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Location: NE Indiana, USA (NTSC)
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?


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PostPosted: Sun Mar 22, 2015 12:37 pm 
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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).

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PostPosted: Sun Mar 22, 2015 2:34 pm 
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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).

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PostPosted: Mon Mar 23, 2015 11:28 pm 
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Thanks, you were probably right, I wasn't doing a proper initialization. :)

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PostPosted: Fri Dec 02, 2016 8:59 pm 
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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.

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