On Tue, 16 Feb 1999, Chris Wilkson wrote:
> The Pitfall II chip was designed (by David Crane?) to be a general
> purpose "helper" chip. Not really a coprocessor, but it's getting
> there. Unfortuantely, it only saw action in Pitfall II.
The only emulator that I am aware of that can run Pitfall II is PCAE. In
the PCAE documentation, the emulator author offers a few hints about the
Pitfall II cartridge. He writes:
"A note about Pitfall II: Lost Caverns: this game, unlike all other Atari
2600 games, has a special chip that contains 2k of extra data in addition
to the standard 8k. It also contains three random number generators and a
three-channel square wave generator. To play Pitfall II on PCAE, the ROM
file must be 10,495 bytes in size. The first 8k must be the standard 8k
dump of the main ROM chip; the next 2048 bytes must consist of the 2k of
extra data in the special chip, and the last 255 bytes must be read from
one of the random number generators (the three random number generators
each have a 255-byte cycle and produce the same values). Such a ROM file
encompasses all the data that can be generated from the cartridge; PCAE is
designed to automatically read whichever part is appropriate, depending on
the addresses accessed."
PCAE does quite a good job of running Pitall II. The source code to the
emulator is available, too, so it would be possible to examine PCAE to see
how it emulates Pitfall II to understand how the cartridge works.
PCAE (and source code) can be found at:
http://www.classicgaming.com/pcae/
Paul Hart
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