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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.uwa.edu.au!classic.iinet.com.au!swing.iinet.net.au!news.uoregon.edu!chi-news.cic.net!simtel!swidir.switch.ch!scsing.switch.ch!news.belwue.de!news.uni-ulm.de!rz.uni-karlsruhe.de!news.uni-stuttgart.de!uni-regensburg.de!lrz-muenchen.de!faui0n.informatik.uni-erlangen.de!uni-erlangen.de!news.tu-chemnitz.de!irz401!uriah.heep!not-for-mail From: j@uriah.heep.sax.de (J Wunsch) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Q: FreeBSD 1.1.5.1 motherboard swap 486->386, system won't boot! Date: 29 Oct 1995 18:13:59 +0100 Organization: Private FreeBSD site, Dresden. Lines: 21 Message-ID: <470con$192@uriah.heep.sax.de> References: <46kj1d$e3l@nntp5.u.washington.edu> <DH1vK9.D6@theatre.pandora.sax.de> NNTP-Posting-Host: uriah.heep.sax.de Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Martin Welk <mw@theatre.pandora.sax.de> wrote: >Please don't ask me which advanced features of the 486 CPU are >used by FreeBSD, I don't know (and I'm not sure if I wanne know :-) ) >Perhaps some of the gurus here can answer that? The 386 CPU had a very poor design flaw: you couldn't write-protect kernel (``privilege level 0'') pages. This makes implementinnng copy-on-write rather difficult. (It can be done by a workaround, as there used to be a workaround for the design flaw of the Vax MMU where they ``forgot'' to implement a `page referenced' bit. :) This has been fixed in the 486. There are a few potentiall interesting features of a 586 either, that make it worth to differentiate between the CPU types. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)