From: joe@jshark.rn.com
Subject: Re: LINUX is obsolete
Date: 31 Jan 92 13:21:44 GMT
Organization: a blip of entropy
In article <12595@star.cs.vu.nl> ast@cs.vu.nl (Andy Tanenbaum) writes:
>
> MINIX was designed to be reasonably portable, and has been ported from the
> Intel line to the 680x0 (Atari, Amiga, Macintosh), SPARC, and NS32016.
> LINUX is tied fairly closely to the 80x86. Not the way to go.
If you looked at the source instead of believing the author, you'd realise
this is not true!
He's replaced 'fubyte' by a routine which explicitly uses a segment register
- but that could be easily changed. Similarly, apart from a couple of places
which assume the '386 MMU, a couple of macros to hide the exact page sizes
etc would make porting trivial. Using '386 TSS's makes the code simpler,
but the VAX and WE32000 have similar structures.
As he's already admitted, a bit of planning would have the the system
neater, but merely putting '386 assembler around isn't a crime!
And with all due respect:
- the Book didn't make an issue of portability (apart from a few
"#ifdef M8088"s)
- by the time it was released, Minix had come to depend on several
8086 "features" that caused uproar from the 68000 users.
>Andy Tanenbaum (ast@cs.vu.nl)
joe.
From: entropy@wintermute.WPI.EDU (Lawrence C. Foard)
Subject: Re: LINUX is obsolete
Date: 5 Feb 92 14:56:30 GMT
Organization: Worcester Polytechnic Institute
In article <12595@star.cs.vu.nl> ast@cs.vu.nl (Andy Tanenbaum) writes:
>Don`t get me wrong, I am not unhappy with LINUX. It will get all the people
>who want to turn MINIX in BSD UNIX off my back. But in all honesty, I would
>suggest that people who want a **MODERN** "free" OS look around for a
>microkernel-based, portable OS, like maybe GNU or something like that.
I believe you have some valid points, although I am not sure that a
microkernel is necessarily better. It might make more sense to allow some
combination of the two. As part of the IPC code I'm writting for Linux I am
going to include code that will allow device drivers and file systems to run
as user processes. These will be significantly slower though, and I believe it
would be a mistake to move everything outside the kernel (TCP/IP will be
internal).
Actually my main problem with OS theorists is that they have never tested
there ideas! None of these ideas (with a partial exception for MACH) has ever
seen the light of day. 32 bit home computers have been available for almost a
decade and Linus was the first person to ever write a working OS for them
that can be used without paying AT&T $100,000. A piece of software in hand is
worth ten pieces of vaporware, OS theorists are quick to jump all over an OS
but they are unwilling to ever provide an alternative.
The general consensus that Micro kernels is the way to go means nothing when
a real application has never even run on one.
The release of Linux is allowing me to try some ideas I've been wanting to
experment with for years, but I have never had the opportunity to work with
source code for a functioning OS.
From: ast@cs.vu.nl (Andy Tanenbaum)
Subject: Re: LINUX is obsolete
Date: 5 Feb 92 23:33:23 GMT
Organization: Fac. Wiskunde & Informatica, Vrije Universiteit, Amsterdam
In article <1992Feb5.145630.759@wpi.WPI.EDU> entropy@wintermute.WPI.EDU (Lawrence
C. Foard) writes:
>Actually my main problem with OS theorists is that they have never tested
>there ideas!
I'm mortally insulted. I AM NOT A THEORIST. Ask anybody who was at our
department meeting yesterday (in joke).
Actually, these ideas have been very well tested in practice. OSF is betting
its whole business on a microkernel (Mach 3.0). USL is betting its business
on another one (Chorus). Both of these run lots of software, and both have
been extensively compared to monolithic systems. Amoeba has been fully
implemented and tested for a number of applications. QNX is a microkernel
based system, and someone just told me the installed base is 200,000 systems.
Microkernels are not a pipe dream. They represent proven technology.
The Mach guys wrote a paper called "UNIX as an application program."
It was by Golub et al., in the Summer 1990 USENIX conference. The Chorus
people also have a technical report on microkernel performance, and I
coauthored another paper on the subject, which I mentioned yesterday
(Dec. 1991 Computing Systems). Check them out.
Andy Tanenbaum (ast@cs.vu.nl)
