[atari7800] Re: SpaceWar! 7800 update

> of the Keith Henrickson/Daniel Boris disassembly confirmed it - starting
at
> $F8E7 the BIOS runs a full RAM test which fails because the 2600 cart is
> shadowed at $1800-$1F00.

Actually, I later realized that the cartridge is disabled at that point in
the code.  But later the BIOS copies the digital signature to both $1901 and
$2000, so I bet that kills it there.

Although I haven't gone through all of it, but the BIOS is a wierd bit of
code.  In addition to the full RAM test, there is a fairly complete test of
the 6502 itself.  (It looks like it was designed to interface with some kind
of diagnostic cartridge.)  The code also jump around a lot for no
immediately apparent reason.  Maybe it was written in chunks by different
people, or parts got included in over time.  The fact that a bunch of the
code is copied to RAM first also makes it tougher to follow.

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