From owner-freebsd-questions@FreeBSD.ORG Tue Jun 13 11:17:59 2006 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9A8CB16A4D7 for ; Tue, 13 Jun 2006 11:17:59 +0000 (UTC) (envelope-from otto@drijf.net) Received: from vera.drijf.net (vera.xs4all.nl [213.84.84.111]) by mx1.FreeBSD.org (Postfix) with ESMTP id D3A0C43D48 for ; Tue, 13 Jun 2006 11:17:58 +0000 (GMT) (envelope-from otto@drijf.net) Received: from fonzo.intra.drijf.net (otto@fonzo.intra.drijf.net [10.0.1.12]) by vera.drijf.net (8.13.6/8.13.4) with ESMTP id k5DBHULN031060 (version=TLSv1/SSLv3 cipher=DHE-DSS-AES256-SHA bits=256 verify=NO); Tue, 13 Jun 2006 13:17:31 +0200 (CEST) Date: Tue, 13 Jun 2006 13:17:30 +0200 (CEST) From: Otto Moerbeek X-X-Sender: otto@fonzo.intra.drijf.net To: Johnny Billquist In-Reply-To: <448E8D23.5030008@update.uu.se> Message-ID: References: <448E8D23.5030008@update.uu.se> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Mailman-Approved-At: Tue, 13 Jun 2006 11:51:10 +0000 Cc: John Nemeth , misc@openbsd.org, Ted Unangst , Ted Mittelstaedt , freebsd-questions@freebsd.org, =?ISO-8859-1?Q?H=E1morszky_Bal=E1zs?= , netbsd-users@NetBSD.org, Nikolas Britton Subject: Re: wikipedia article X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 13 Jun 2006 11:17:59 -0000 On Tue, 13 Jun 2006, Johnny Billquist wrote: > Otto Moerbeek wrote: > > On Mon, 12 Jun 2006, Ted Mittelstaedt wrote: > > > > > > > > -----Original Message----- > > > > From: John Nemeth [mailto:jnemeth@victoria.tc.ca] > > > > Sent: Monday, June 12, 2006 1:15 PM > > > > To: Ted Mittelstaedt; Nikolas Britton; Ted Unangst > > > > Cc: Hamorszky Balazs; misc@openbsd.org; freebsd-questions@freebsd.org; > > > > netbsd-users@NetBSD.org > > > > Subject: RE: wikipedia article > > > > > > > > > > > > On Nov 1, 6:11pm, "Ted Mittelstaedt" wrote: > > > > } > > > > } Prior to the release of the 80386 the Intel processors didn't have > > > > } memory protection which was a requirement of any processor running > > > > } the BSD kernel. > > > > > > > > This is not entirely true. The 80286 had memory protection. > > > > However, its memory protection was completely based on segments (i.e. > > > > it could not do paging). > > > > > > Oh, yeah, your right about that. Me bad. > > > > > > > > > > Also, it was only a 16 bit processor. > > > > > > What was the bit size of the CPU's originally used to write UNIX in Bell > > > Labs? > > The PDP-7 was/is an 18-bit machine. > > > What's more, iirc the MMU of the pdp11 isn't what we call a MMU today, > > it could not even do paging. > > You're wrong. You could easily do paging on a PDP-11, if you wanted to. The > main reasons this wasn't done are two. > 1) Each page is 8K. At the time, that was considered way too large pages for a > demand page system. > 2) The address space is only 64 per process, which means you only have 8 > pages. Not only is that perhaps a little little for meaningful paging (most > programs tend to refer to all 8 pages most of the time). The main memory on a > PDP-11 is furthermore 4 meg, so having a lot of processes full memory space in > physical memory at the same time is not a problem. > > The PDP-11 MMU is a beatiful MMU. Nothing like the crap Intel spits out. ;-) I stand corrected. I always thought it coulnd't do paging, but I suppose it should be "due to various restrictions, it couldn't do meaningful paging". -Otto