From owner-freebsd-hackers Thu Jun 21 20:51:55 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from saturn.bsdhome.com (unknown [24.25.2.193]) by hub.freebsd.org (Postfix) with ESMTP id 51CF937B401 for ; Thu, 21 Jun 2001 20:51:52 -0700 (PDT) (envelope-from bsd@bsdhome.com) Received: from neutrino.bsdhome.com (jupiter [192.168.220.13]) by saturn.bsdhome.com (8.11.3/8.11.3) with ESMTP id f5M3poL20745; Thu, 21 Jun 2001 23:51:50 -0400 (EDT) Received: (from bsd@localhost) by neutrino.bsdhome.com (8.11.4/8.11.4) id f5M3piW00566; Thu, 21 Jun 2001 23:51:44 -0400 (EDT) (envelope-from bsd) Date: Thu, 21 Jun 2001 23:51:44 -0400 From: Brian Dean To: Jonathan Lemon Cc: mikulas@artax.karlin.mff.cuni.cz, hackers@FreeBSD.ORG Subject: Re: Patented algorithm in FreeBSD Message-ID: <20010621235144.A367@neutrino.bsdhome.com> References: <200106112237.f5BMbuh06004@prism.flugsvamp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <200106112237.f5BMbuh06004@prism.flugsvamp.com>; from jlemon@flugsvamp.com on Mon, Jun 11, 2001 at 05:37:56PM -0500 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Mon, Jun 11, 2001 at 05:37:56PM -0500, Jonathan Lemon wrote: > Hmm, let's see: > > Assignee: Digital Equipment Corporation (Maynard, MA) > Appl. No.: 646734 > Filed: May 3, 1996 > > Versus: > > * Derived from hp300 version by Mike Hibler, this version by William > * Jolitz uses a recursive map [a pde points to the page directory] to > * map the page tables using the pagetables themselves. This is done to > * reduce the impact on kernel virtual memory for lots of sparse address > * space, and to reduce the cost of memory to each process. > * > * from: hp300: @(#)pmap.h 7.2 (Berkeley) 12/16/90 > * from: @(#)pmap.h 7.4 (Berkeley) 5/12/91 > > So it looks like we have prior art by around 6 years, which would > invalidate the patent iff it was the same thing. [rummaging through my old box of manuals... Aha!] This also appears to be _very_ similar to the scheme described by Intel themselves in a skinny little book entitled "80386 System Software Writer's Guide", ISBN 1-55512-023-7, Intel order number 231499-001. This book is dated 1987 and describes the handy recursive page table mapping starting at the bottom of page 2-18. -Brian To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message