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Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!msuinfo!netnews.upenn.edu!news.amherst.edu!news.mtholyoke.edu!news.byu.edu!news.kei.com!MathWorks.Com!europa.eng.gtefsd.com!library.ucla.edu!ihnp4.ucsd.edu!network.ucsd.edu!keyhole.ucsd.edu!not-for-mail From: eld@keyhole.ucsd.edu (Eric Dorman) Newsgroups: comp.os.386bsd.questions Subject: Re: 386 VS 286 Date: 15 Apr 1994 12:35:36 -0700 Organization: MPL of SIO at UCSD Lines: 51 Sender: eld@mpl.ucsd.edu Message-ID: <2omqa8$ph9@keyhole.ucsd.edu> References: <1994Apr11.194516.513@roadie.uucp> <2odjg2$i2p@keyhole.ucsd.edu> <2oh12o$2vs@starlight.datlog.co.uk> NNTP-Posting-Host: keyhole.ucsd.edu >Eric Dorman (eld@keyhole.ucsd.edu) wrote: >: From chiyoko@knight.ice.sda.cbis.com Tue Apr 12 00:31:42 PDT 1994 > >: >What type of write polyicy does a typical 286 processor implement? >: As far as I know no commercial segmented-VM system was ever released >: for the '286s. It's really not that hard to implement (i've done it) > >Didn't this get done by Microsoft/SCO with Xenix and also by Microsoft/IBM >with OS/2 1.0 ??? (Maybe also Digital Research with MP/M ?) I'm prettu sure no Xenix variant had demand-segments. Dunno about MP/M but i think that never got past swapping entire processes either (it was pretty dead by the time '286s came out, I recall) Wouldn't know about OS/2; mostly a unix house here :) >: but it seemed that people were more interested in whining about the >: '286s architecture than writing programs that worked :) On my hardware >I seem to recall a lot of people complaining about paging operations causing >a massive overhead... (I didn't get close to it, so memory hazy). >I do remember the reason a lot of people went SCO XENIX -> Unix was for >greater performance with large numbers of users (Paging activity not >anywhere near as expensive, Unix being implemented for i386, whilst the Xenix >system still ran in protected mode at that time - moved an accountancy system >myself because of this). Most apps we had needed to be restructured to work well with the segmented architecture; some things can't be done well because of the segment-table reads, so you took a performance hit with large (>64k) arrays and large link-lists. It's just much easier to write for flat-model machines like VAXen and ix86s:x>=3. Demand segmentation takes a hit from having to write out 64k segments rather than 1k or 4k pages. At the time the Intel Multibus I machines had 2x/3x the transfer rate to disk (killer I/O!) so it wasn't a big deal. We were source licencees for Unix V.2 '286 (the old Microport porting base) so there was plenty of code to play with. Pity PCs got so cheap so fast...my old multibus hardare still works! Can't get software support anymore... [deleted] : Intel architectures are character-building! >!!! :) : >Chiyoko Koike Miklasevich : Eric Dorman >Kevin Graham. Data Logic Limited >Systems Engineer CI Tower, St Georges Square, High Street, >kgraham@datlog.co.uk New Malden, Surrey, England KT3 4HH >Tel: +44 (0)81 715 9696 x414 Fax: +44 (0)81 715 1771 >Systems, network and internet support for the Makurokuroski...