Path: utzoo!attcan!uunet!mcvax!cernvax!ethz!forty2!poole
From: poole@forty2.UUCP (Simon Poole)
Newsgroups: comp.sys.atari.st
Subject: Re: Register saving for BIOS traps?
Message-ID: <469@forty2.UUCP>
Date: 25 Sep 88 20:20:18 GMT
References: <19880922163903.5.JRD@MOA.SCRC.Symbolics.COM>
Reply-To: poole@forty2.UUCP (Simon Poole)
Organization: Exp. Physics University Zuerich
Lines: 22

In article <19880922163903.5.JRD@MOA.SCRC.Symbolics.COM> jrd@STONY-BROOK.SCRC.SYMBOLICS.COM (John R. Dunning) writes:
.....
>I believe it's necessary to save (some) registers around BIOS and XBIOS
>traps.  The question for today is: which ones?  Is there any rhyme or
>reason to which registers get trashed inside the trap?

D0-D2 and A0-A2,  reason: they aren't  saved by the  trap handler, but
are used by the calls, why Atari decided not to save all regs they use
is a mystery to me (the calls are so slow just because they save nearly
everthing, it seems a shame they didn't do it all).

>A related question; am I correct in assuming that GEMDOS traps don't
>require register saving?

I wouldn't count on that, suposedly D0 and A0 get zapped (I don't have
the official Atari doc's lying around here, but I'll check on Monday).


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