Capcom Classics Mini Mix

Discuss emulation of the Nintendo Entertainment System and Famicom.

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NewRisingSun
Posts: 1286
Joined: Thu May 19, 2005 11:30 am

Re: Capcom Classics Mini Mix

Post by NewRisingSun » Sun Feb 14, 2021 1:37 am

lidnariq wrote:
Sat Feb 13, 2021 7:25 pm
For my own curiosity, what's the changes in behavior of these rereleases? Are they different from the original games? Or are the new instructions just to get in the way of extracting the ROMs and using them in a general purpose emulator?
  1. Some fonts were modified to look better on the GBA's smaller-resolution screen.
  2. A few key code locations have been changed by replacing opcodes:
    • sequence 88 D0 FD CA D0 FA to FA EA EA EA EA EA in a single spot,
    • opcode 8D to FB in a single spot,
    • opcode E8 to FC in a single spot,
    • opcode A5 to FF in a single spot.

tepples
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Location: NE Indiana, USA (NTSC)
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Re: Capcom Classics Mini Mix

Post by tepples » Sun Feb 14, 2021 7:02 am

The first of these code changes replaces a delay loop with a specific 1-byte NOP, presumably a command to tell the emulated memory controller to pause the CPU until something happens.

Code: Select all

@loop:
  dey
  bne @loop
  dex
  bne @loop

NewRisingSun
Posts: 1286
Joined: Thu May 19, 2005 11:30 am

Re: Capcom Classics Mini Mix

Post by NewRisingSun » Sun Feb 14, 2021 7:09 am

That delay loop is what makes the Bionic Commando title screen reveal itself line-by-line.

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