Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!utah-gr!uplherc!sp7040!obie!wes
From: wes@obie.UUCP (Barnacle Wes)
Newsgroups: comp.sys.atari.st
Subject: Re: To Fix or Not To Fix (Really: applying patches to OS)
Summary: But YOU have missed the point, too!
Message-ID: <169@obie.UUCP>
Date: 25 Aug 88 15:14:07 GMT
References: <635@ihnet.ATT.COM> <383@snjsn1.SJ.ATE.SLB.COM> <1224@netmbx.UUCP> <530@nikhefh.hep.nl>
Organization: the Well of Souls
Lines: 22

In article <530@nikhefh.hep.nl>, gert@nikhefh.hep.nl (Gert Poletiek) writes:
> If Atari would do things this way (and I doubt there is any look/feel
> involved) you could easily work with different versions of Malloc() in the
> same system.

Gert, you have missed the point.  You can easily patch GEMDOS, BIOS, or
XBIOS functions on the ST - the new routine saves the original trap
address, installs itself as the trap handler.  Whenever it is called, it
checks to see if the function number is the one it handles, and if not,
passes the call off to the original vector.  This can be done via a
program in the \AUTO folder, even.

This is not quite as elegant as the Line A trap, but it does work, and
the Line A & F traps were designed for other reasons.  On the '020 and
'030, Line A opcodes are MMU ('851 for the '020, built-in on the '030)
instructions, and Line F opcodes are FPU ('881 or '882) instructions.

-- 
                     {hpda, uwmcsd1}!sp7040!obie!wes
           "Happiness lies in being priviledged to work hard for
           long hours in doing whatever you think is worth doing."
                         -- Robert A. Heinlein --