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From: jbn@glacier.STANFORD.EDU (John B. Nagle)
Newsgroups: comp.sys.amiga
Subject: Re: The Next Generation
Message-ID: <17218@glacier.STANFORD.EDU>
Date: Fri, 13-Nov-87 12:05:11 EST
Article-I.D.: glacier.17218
Posted: Fri Nov 13 12:05:11 1987
Date-Received: Sun, 15-Nov-87 09:32:50 EST
References: <2785@megaron.arizona.edu>
Reply-To: jbn@glacier.UUCP (John B. Nagle)
Organization: Stanford University
Lines: 33


    1.  Given the way that RAM prices are declining while
	disk access times are not improving, virtual memory
	looks like an idea whose time has passed.  Most newer
	systems with virtual memory use it as an excuse for
	fat software.  Sun and Symbolics are the worst offenders
	in this regard.   (Sun users: try "size /bin/ps".  Then
	try to think of what could possibly make it that big.)

    2.  "Lightweight processes" are an old idea, not a new one.  
	EXEC 8 for the Univac 1108 and its successors have had them
	since 1969; so have some other mainframe systems.  It's
	merely the fact that the operating systems whose
	internals are well-known in the academic community,
	TOPS-20 and UNIX, don't have them that makes people
	think that they have invented something new.  

    3.  Memory protection is desirable, but a true protected operating
	system would require that the operating system keep track of
	all the resources requested by a user program and be able
	to take them back when a program exited abnormally.  Tripos
	(alias AmigaDos) does not do the bookeeping to allow this.
	Neither does the system in the Mac line.  We don't yet have
	a widely used example of an efficient operating system for
	small machines that provides proper protection.  However,
	OS/2 for the IBM PS/2 supposedly meets this criterion.
	We will have to see.  Note that if it does, users will soon
	find it intolerable for their machine to crash all the
	time like present generation systems.  All the other vendors
	will then have to catch up with IBM.


					John Nagle