Path: utzoo!mnetor!uunet!husc6!bbn!uwmcsd1!ig!jade!saturn!ssyx!koreth
From: koreth@ssyx.ucsc.edu (Steven Grimm)
Newsgroups: comp.sys.atari.st
Subject: Re: Multitasking??
Message-ID: <1479@saturn.ucsc.edu>
Date: 23 Dec 87 17:35:57 GMT
References: <8712221448.AA21644@ucbvax.Berkeley.EDU> <39@lzaz.ATT.COM>
Sender: usenet@saturn.ucsc.edu
Reply-To: koreth@ssyx.ucsc.edu (Steven Grimm)
Organization: The American Redundancy Society of America
Lines: 21

In article <39@lzaz.ATT.COM> bds@lzaz.ATT.COM (BRUCE SZABLAK) writes:
>Frankly, if the BIOS was written re-enterantly, there would be
>little difficulty in adding multitasking. It could be done for
>those who use it, and those who didn't could ignore it.

The ST's BIOS is re-entrant.  GEMDOS is not.  (I have a multiuser BBS
system to prove it...)  You just have to make sure that each task has
its own BIOS register save area.  That took me a while to figure out --
basically you switch the BIOS stack pointer in your task-switching
routine, as well as the user stack pointer and all the registers.
Multitasking on the ST is actually fairly trivial, as long as you don't
try to use Pexec() or Pterm().  I'm working on rewriting both of those
right now for the background Xmodem accessory in ST-Talk Professional.

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