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From: koreth@ssyx.ucsc.edu (Steven Grimm)
Newsgroups: comp.sys.atari.st
Subject: Re: To Fix or Not To Fix (Really: applying patches to OS)
Message-ID: <4582@saturn.ucsc.edu>
Date: 22 Aug 88 22:09:37 GMT
References: <635@ihnet.ATT.COM> <383@snjsn1.SJ.ATE.SLB.COM> <1224@netmbx.UUCP> <524@nikhefh.hep.nl>
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Reply-To: koreth@ssyx.ucsc.edu (Steven Grimm)
Organization: The Mad Scientists' Guild
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In article <524@nikhefh.hep.nl> gert@nikhefh.hep.nl (Gert Poletiek) writes:
>Look at the way things are organized in the Macintosh OS. All system traps
>are routed by a trap address table (just like in GemDos). The subtle
>difference with GemDos is that the trap address table is located somewhere in
>RAM, not ROM. (Well, it is copied from ROM to RAM at system boot time).

The ST's trap vectors are in RAM, too.  In fact, I don't know of *ANY* 68xxx
box that doesn't have them in RAM.  Their locations are down in low memory
($60 or thereabouts, I don't remember exactly...)  You have to be in supervisor
mode to write to them, but they can certainly be changed.  I've done it lots
of times.

>The Mac OS has two calls (GetTrapAddress and SetTrapAddress) which get and
>set a trap vector in the traps table (resp).

Try looking up Setexc() in your XBIOS manual.

---
These are my opinions, and in no way reflect those of UCSC, which are wrong.
Steven Grimm		Moderator, comp.{sources,binaries}.atari.st
koreth@ssyx.ucsc.edu	uunet!ucbvax!ucscc!ssyx!koreth