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From: gillies@p.cs.uiuc.edu
Newsgroups: comp.sys.amiga
Subject: Re: Multi-tasking and OS books
Message-ID: <129000003@p.cs.uiuc.edu>
Date: 17 May 89 05:10:00 GMT
References: <17195@usc.edu>
Lines: 17
Nf-ID: #R:usc.edu:17195:p.cs.uiuc.edu:129000003:000:780
Nf-From: p.cs.uiuc.edu!gillies    May 17 00:10:00 1989


> Re: Multitasking
> 	To be able to do premptive scheduling *efficiently*, the OS must be 
> designed for it.  The Amiga's was designed for it.  The IBMs and MACs OS were
> not and you can see the mess they have to deal with now.

The main thing you want/need is a frequent repeating clock interrupt.
The PC rots because (I think) the original interrupt was only 18 times
per second (~55ms timeslice minimum).  The Mac's interrupt is 60 times
a second (vertical retrace interrupt) -- much more reasonable.  A
decent timeslice on today's multi-mips machines is 10-25 millisecs.
(40-100 interrupts/second).


Don Gillies, Dept. of Computer Science, University of Illinois
1304 W. Springfield, Urbana, Ill 61801      
ARPA: gillies@cs.uiuc.edu   UUCP: {uunet,harvard}!uiucdcs!gillies