XINU Update

[dog_cow@macgui.com (D Finnigan)]

Some people might remember me doing some blabbering a few months ago about
trying to get the Xinu code, which was, by strange twist of fate, written
for an Apple clone (the CAT) which used a non-standard bank-switching
scheme.

After figuring out how to work the LISA v2.5 assembler, and learning more
assembly language, I have managed to make the necessary modifications to get
it to load to the point of the shell, wherein commands may be entered. I
have not done anything with attempting to get the file system to work.

However, I make this post to bring to light the fact that if anyone is
looking for a fairly simple programming project which could be completed in
either a weekend or a week, depending on your skill and how much time you
put into it, fixing up the Xinu code is something fairly straight-forward
and easy to do. What took me the longest was actually reading over the code
and understanding how it worked. Fortunately, it is well-commented.

The changes I have made are, briefly:
- removing all references to the CAT memory bank-switching
- changing memory locations to bring Xinu out of the language card area
- fixing a (bug?) spot in the code where a Monitor routine is called, but
the LC RAM was active, resulting in a hang

Moving the code down in RAM does result in less RAM being available for the
user-land processes (of which there is exactly one at this point-- the
shell) but does simplify things. A further project would be to put the
kernel and ProDOS disk driver in language card RAM and switch as needed. I
have not gotten to that point yet.

-- 
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computing.
http://macgui.com/vault/