Re: [stella] Weird Donkey Kong disassembly prob

Subject: Re: [stella] Weird Donkey Kong disassembly prob
From: Thomas Jentzsch <tjentzsch@xxxxxx>
Date: Fri, 2 Apr 2004 09:29:57 +0200
Paul Slocum wrote:

> So I did a file diff on the original Donkey Kong ROM and the one produced
> from the disassembly.  I found 6 differences in the file, and all were
> because the original game reads from input ports using $30 as the base
> input address and vcs.h puts the base at $00.  I changed vcs.h to use the
> base address $30, and then the game worked fine on a real 2600.  I have no
> idea why.

Those differences are probably resulting from different collision
registers addresses. There only the two top most bits are defined and
IIRC the other six are depending on the current CPU bus read address.
Maybe Donkey Kong expects some values in those 6 bits.

Have fun!
Thomas Jentzsch         | *** Every bit is sacred ! ***
tjentzsch at web dot de |

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