From owner-freebsd-questions@FreeBSD.ORG Tue Jun 13 10:02:21 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 C0D4816A41B for ; Tue, 13 Jun 2006 10:02:21 +0000 (UTC) (envelope-from bqt@update.uu.se) Received: from GW.SoftJAR.SE (205.225.216.81.static.spa.vf.siwnet.net [81.216.225.205]) by mx1.FreeBSD.org (Postfix) with ESMTP id 1572843D49 for ; Tue, 13 Jun 2006 10:02:20 +0000 (GMT) (envelope-from bqt@update.uu.se) Received: from [10.0.0.13] (213-65-173-246-no96.tbcn.telia.com [213.65.173.246]) by GW.SoftJAR.SE (Postfix) with ESMTP id 6176362741; Tue, 13 Jun 2006 12:02:16 +0200 (CEST) Message-ID: <448E8D23.5030008@update.uu.se> Date: Tue, 13 Jun 2006 12:02:11 +0200 From: Johnny Billquist Organization: Update Computer Club User-Agent: Mozilla Thunderbird 1.0.7 (Windows/20050923) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Otto Moerbeek References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Tue, 13 Jun 2006 11:50:40 +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 10:02:21 -0000 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. ;-) Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt@update.uu.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol