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Subject: Submission for mod-computers-68k
Message-ID: <8702142156.AA18541@castor.usc.edu>
Date: Sat, 14-Feb-87 16:56:19 EST
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Posted: Sat Feb 14 16:56:19 1987
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Path: castor.usc.edu!blarson
From: blarson@castor.usc.edu (Bob Larson)
Newsgroups: mod.computers.68k
Subject: Re: OS9 Questions (was Re: Minix/68k)
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Date: 14 Feb 87 21:56:18 GMT
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In article <8702130559.AA20439@tilde> bill@caip.rutgers.edu@tifsie.UUCP (Bill Stoltz) writes:

Os9/68k:

>If every process is position independent then is every process limited
>to 64K bytes?  In order to be position independent you have to use
>PC relative code.  PC relative, from what I have been able to find,
>is +-32K bytes.  Obviously, programs can be greater than 64k but all
>references must be within 32k.  How does OS9 handle this?

Local program references are limited to the PC-relitive limits.
External references are fixed by the linker to inderection through
initalized data.  (The run-time initialization code calculates the
actual address.) Warning: the linker that came with the 2.0 C compiler
had a bug in how it handled pointers to functions more than 32kbytes
away. 

>What does OS9 use to try to protect other processes or kernel memory
>from the currently running process, without the use of an MMU?

Without hardware assistance, there is not much it can do.  The fact
that all of os9 is relocatable and may be in different places based on
machine, os version, etc. does help keep the tinkerers at bay.
 
>Where can I get more information on OS9?  (General Overview and
>some internal workings like we have discussed here)?

Os9/6809 is covered pretty well in "the complete rainbow guide to
os9".  (Available at radio shack.) The 68k version is similar, but
improved.  68 micro journal is the only non-coco commercial magazine
that gives regular coverage to os9.  The Os9 users group occasionaly
gets around to putting out another issue of their "monthly" magazine
MOTD.  (I don't have their new address.) Mod.os.os9 has some
interesting stuff once in a while.  Compuserve has a pretty active,
but non-technical, os9 section.  Bix and Delphi also have os9
sections.  (The delphi one is shoved under their coco section.) I'm
sure microware would be willing to sell you a set of manuals. 

-- 
Bob Larson
Arpa: Blarson@Usc-Eclb.Arpa
Uucp: (several backbone sites)!sdcrdcf!usc-oberon!castor.usc.edu!blarson
			seismo!cit-vax!usc-oberon!castor.usc.edu!blarson