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update Atari description

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git-svn-id: svn://svn.cc65.org/cc65/trunk@3572 b7a2c559-68d2-44c3-8de9-860c34a00d81
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cpg 2005-08-07 21:00:40 +00:00
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doc/internal.txt
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@ -155,22 +155,15 @@ APPLE2: The program starts at $800, end of RAM is $8E00, so 33.5K of memory
(including stack) are available.
Atari: The startup code will adjust the upper memory limit to the installed
memory, considering future graphics memory usage (which is allocated
at top of RAM). The programmer can specify which graphics mode is
about to be used by defining a variable _graphmode_used, unsigned
char, to the mode value (mode values like Atari DOS, 0-31).
(Please note that graphics mode selection isn't supported in the
Atari runtime lib yet!)
In the default case the upper memory limit will be $8035 (with Basic
cartridge) and $A035 (without cartridge). This is the default which
leaves room for the biggest possible graphics mode. If only standard
text mode is used (_graphmode_used = 0), the values are $9C1F (with
Basic) and $BC1F (no cartridge).
The program starts at $1F00 (to leave room for DOS), and the free
memory values are $6135 (24K, Basic, default mode), $8135 (32K, no
Basic, default mode), $7D1F (31K, Basic, mode 0) and $9D1F (39K,
no Basic, mode 0).
These values are for a 48K or 64K machine.
memory detected at runtime. The programmer can adjust the upper memory
limit by setting the __RESERVED_MEMORY__ variable at link time. The
given __RESERVED_MEMORY__ value will be subtracted from the upper
memory limit used by the runtine. This memory could be used as graphics
memory, for example.
In the default case (no setting of __RESERVED_MEMORY__) the upper
memory limit is $9C1F (with Basic cartridge) and $BC1F (without
cartridge). The program starts at $2E00 by default.
These values are for a 48K or 64K machine.
Note: The above numbers do not mean that the remaining memory is unusable.
However, it is not linear memory and must be accessed by other, nonportable