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column
5, line 3
CPU 10 is obviously the
CD CPU...
column
5, line 5
...hence, CPU 14 is the
Genesis CPU. The image processing unit 16 is the Genesis VDP.
column
5, line 11
Very important. It seems
that if the 512kb of memory which the Sega CD has is divided into two parts.
The memory handling seems to be a bit strange. According to the text, each
CPU (Genesis and CD) can access only ONE half of the memory. The data exchange
between the two parts of the memory is done by a gate array unit, explained
later in the text.
column
5, line 43 & 50
The text says it: Don´t
let yourself be confused by the diagrams which were mentioned in the last
part of the text, because the writers only gave an example of how the CD
CPU can be used.
column
6, lines 7-37
This is in my opinion
the most important part of the document. The whole process of CD CPU computing,
memory management by the gate array and the Genesis CPU is described here.
You have to read it carefully, though. The CPU 100 is the CD CPU. CPU 101
is the Genesis CPU. The "switch" has to be some control register which
the games should use quite often, because the "switch" is used to exchange
data between the CD and Genesis memory. Memory 121 which only the CD CPU
can access is maybe the CD-ROM drive´s cache memory.
Be aware of the fact
that whenever there is spoken of "image processing" in the text, that this
doesn´t mean that the CD CPU can do only graphics processing. The
CD CPU can do all kinds of calculations during that time!
column
6, lines 38-45
Parallel processing is
possible.
column
6, lines 55ff
Explains the different
parts of the BIOS. Very important when tracking down all the BIOS funtions.