Date: Mon, 11 Jun 2001 17:37:56 -0500 (CDT) From: Jonathan Lemon <jlemon@flugsvamp.com> To: mikulas@artax.karlin.mff.cuni.cz, hackers@freebsd.org Subject: Re: Patented algorithm in FreeBSD Message-ID: <200106112237.f5BMbuh06004@prism.flugsvamp.com> In-Reply-To: <local.mail.freebsd-hackers/Pine.LNX.3.96.1010611235853.12928A-100000@artax.karlin.mff.cuni.cz>
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In article <local.mail.freebsd-hackers/Pine.LNX.3.96.1010611235853.12928A-100000@artax.karlin.mff.cuni.cz> you write: >Hi > >Go to http://www.uspto.gov/patft/, search for patent number 5873127, and >you will find the description of mapping page table entries into virtual >memory via one page directory entry pointing to the page directory itself >- exactly what FreeBSD does with PTDPTDI and APTDPTDI entries on i386. >(including using alternate space as in get_ptbase() in i386/pmap.c to >access page table entries of different processes). 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. (Not that I've read the patent, but typically the invention must meet *ALL* the claims being described; one small deviation and it is considered to be different.) -- Jonathan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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