Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!ukma!tut.cis.ohio-state.edu!cwjcc!neoucom!wtm
From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.amiga
Subject: Re: Multi-tasking and OS books
Summary: Old O/Ses for the PC/XT
Message-ID: <1636@neoucom.UUCP>
Date: 16 May 89 13:52:55 GMT
References: <17148@usc.edu> <24279@agate.BERKELEY.EDU> <18268@cup.portal.com> <5853@cs.Buffalo.EDU>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 20


We ran Xenix 1.something and IBM's PC/IX on some PC/XT systems that
we have as long ago as 1985.  Peemptive scheduling was implemented
in a fashion using one of the 8253 timer channels to send a
periodic interrupt to the kernel (50 Hz, I think).  It more or less
worked, but thrashed miserably when several processes were fighting
over who got to use the 85 mS, 10 meg disk.  Yuck.

On the XT, there is no such thing as demand paged memory, nor is
there memory protection.  The edit/compile cycle proved pretty
tedious, as little slip-ups in pointer arithmetic would crash the
system.  We switched over to using msdos, as there was no advantage
to Xenix in that environment .. and it was much more difficult for
non-guru scientists to manage their systems.  The 640K environment
was also quite restrictive, and the "kernel" of msdos was smaller.
Everybody wanted to run 1-2-3 anyway.


Bill
wtm@impulse.UUCP