[Coco] Brother Jeremy's OS-9 Level 3 (are you out there, Jeremy?)
alsplace at pobox.com
Thu Apr 12 18:52:28 EDT 2007
Microware did OS-9 Level 1 (flat memory model, everything in one
address space), and OS-9 Level 2 (where memory could be remapped).
CoCo 1/2 used Level 1 (64K) and CoCo 3 used the MMU to map in 512K or
beyond in 8K blocks, thus Level 2 memory management.
I am not sure where Level 2 was used outside of the 6809 (original)
version of OS-9. Every other OS-9 and OS-9000 (today just called
OS-9) made by Microware was Level 1 (flat memory model).
Level 3 was the NitrOS-9 gang's way to break up the 64K map a bit
further, giving more memory for processes to use at one time. I ran a
BBS (StG Net) and it REALLY helped -- the system could be loaded and
I could run more commands from the same address space. It took a hit
on performance, but all the 6309 code and other optimizations
probably made it come out similar speed-wise to a stock, unpatched
OS-9 Level 2.
I do not know which "version" current NitrOS-9 uses, but I can't
really think of any reason not to be using the Level 3. I seem to
recall that it split up, if I recall, memory so SCF and maybe other
file managers had their own 64K block. So, instead of all your
drives, etc. having to fit in to 64K, only the base stuff (kernel,
etc.) had to be there, then serial drivers, etc. had their own map. I
forget what the magic was, but I seem to recall it letting me
dynamically load up multiple hard drive drivers and use them, where
before I had to merge them in to my bootfile to have any room left over.
The "Level 2 Upgrade" (which we may have called Level III wayback
when) is a souped up MultiVue, basically.
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