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From: thomps@gitpyr.UUCP
Newsgroups: comp.os.minix
Subject: Re: Response to news and mail
Message-ID: <3034@gitpyr.gatech.EDU>
Date: Wed, 4-Feb-87 20:57:51 EST
Article-I.D.: gitpyr.3034
Posted: Wed Feb  4 20:57:51 1987
Date-Received: Sat, 7-Feb-87 11:39:45 EST
References: <1049@botter.cs.vu.nl> <9490001@hpfclp.HP.COM>
Organization: Georgia Institute of Technology
Lines: 36
Summary: Its possible according to the book

In article <9490001@hpfclp.HP.COM>, diamant@hpfclp.HP.COM (John Diamant) writes:
> Given the 64K limit on the current MINIX compiler, what is the status of
> self-hosting MINIX?  Earlier you claimed that the system can compile
> itself.  Someone else in this group suggested that this may not be true
> because of size limitations.  I understand that even if it works, you won't
> get the same size executables, but is it even possible (for the entire system)?

This answer is based on the book. Andy can correct me if I've misinterpreted
something. The MINIX OS can be recompiled using the MINIX system even
given the 64K limit. It is possible because MINIX is actually three
separate programs. 

1. Process management and I/O tasks. (these are functionally separate but
linked in the same image to facilitate porting to processors that require
all I/O instructions to be executed in protected mode)

2. Memory manager. It runs at a level above process management and would
not need to run in protected mode.

3. File system. ditto 2

Even though MINIX may be rebuilt using the C compiler provided, it was
actually developed under PC/IX which is IBM's PC UNIX. I would not be at
all suprised if the MINIX compiler produces poorer code. My experience
with academic compiler projects and ACK (Amsterdam Compiler Kit) on 
which the MINIX compiler is based would lead me to believe that efficiency
was probably not one of their top priorities. 

The source to the compiler will be sold for 99.95 but god knows what it
will look like having come out of ACK.

-- 
Ken Thompson  Phone : (404) 894-7089
Georgia Tech Research Institute
Georgia Insitute of Technology, Atlanta Georgia, 30332
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