From owner-freebsd-questions@FreeBSD.ORG Thu Oct 21 14:57:32 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2279E1065679 for ; Thu, 21 Oct 2010 14:57:32 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-ew0-f54.google.com (mail-ew0-f54.google.com [209.85.215.54]) by mx1.freebsd.org (Postfix) with ESMTP id 9BEDC8FC1E for ; Thu, 21 Oct 2010 14:57:31 +0000 (UTC) Received: by ewy28 with SMTP id 28so120048ewy.13 for ; Thu, 21 Oct 2010 07:57:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:received:received:date:from:to:subject :message-id:in-reply-to:references:x-mailer:mime-version :content-type:content-transfer-encoding; bh=vvWOEfmVr4WPhfe7kx30qy2UypAVJA5vfN0EZ+wNB5k=; b=HYLJBsYxlwz5ZcsL5ZuvtrokTi1ybEEexxSyw0E0fbxFOGXJS5TYEvyQ6xaTO5EuIj ylkSRtZuDK9LeWh0UO/e3glZx0FsjaRYR3kBcA1gnCJo+h8aQOdrEWQWHWOPpMQQMC+2 B8fzBCwlPy5OEdDVR03AztMUpow1yS4v+JKqM= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=date:from:to:subject:message-id:in-reply-to:references:x-mailer :mime-version:content-type:content-transfer-encoding; b=X0StB9hBZcliRLoQ8GqmYokdryy5Foj5WTbDN9Gln048oAf7fTjGQNQF/WSty1pPSS HX89NuKlWCeEpgDOYxQndftLyxmBriwHsPnWwcZxnxXHecQbANq1CwOcmoqf65Rxl9Wn NekwFyXG8cE/0ON9+5DxuymyaooFrDgYDX1u8= Received: by 10.213.11.18 with SMTP id r18mr8013159ebr.44.1287673050201; Thu, 21 Oct 2010 07:57:30 -0700 (PDT) Received: from gumby.homeunix.com (bb-87-81-140-128.ukonline.co.uk [87.81.140.128]) by mx.google.com with ESMTPS id y15sm1110740weq.6.2010.10.21.07.57.28 (version=SSLv3 cipher=RC4-MD5); Thu, 21 Oct 2010 07:57:29 -0700 (PDT) Date: Thu, 21 Oct 2010 15:57:24 +0100 From: RW To: freebsd-questions@freebsd.org Message-ID: <20101021155724.0eb1c5a1@gumby.homeunix.com> In-Reply-To: <4CC040E7.7090404@qeng-ho.org> References: <20101017143901.GA71132@current.Sisis.de> <20101019074615.GA2183@current.Sisis.de> <20101020022946.GA23035@thought.org> <20101020052601.GA1977@current.Sisis.de> <4cbe9e9a.3qT7q8JUqJxSD8/V%perryh@pluto.rain.com> <20101020165526.GA25310@thought.org> <4CBF21EB.1080003@tundraware.com> <20101020194605.GA78565@stainmore> <4CBF4CB4.6070902@qeng-ho.org> <20101021133844.235fdc72@gumby.homeunix.com> <4CC040E7.7090404@qeng-ho.org> X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; i386-portbld-freebsd8.1) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: Greybeards (Re: Netbooks & BSD) 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: Thu, 21 Oct 2010 14:57:32 -0000 On Thu, 21 Oct 2010 14:32:23 +0100 Arthur Chance wrote: > On 10/21/10 13:38, RW wrote: > > On Wed, 20 Oct 2010 21:10:28 +0100 > > Arthur Chance wrote: > > > > > >> 50s) had the experience of programming microcode on a machine by > >> inserting brass slugs for 0s and ferrite slugs for 1s on a pin > >> board. > > > > I wonder why it was brass/ferrite rather than brass/empty or > > ferrite/empty. > > Dredging up physics unused for 30+ years, ferrite is ferromagnetic > and intensifies magnetic fields so a coil of wire with ferrite inside > is a massively bigger inductor then an empty coil. I vaguely remember > that brass is slightly diamagnetic, but could be mistaken. If it is, > then it would have the opposite effect and reduce the inductance, so > you'd get a better difference in signal between brass/ferrite than > air/ferrite. Possibly. I'm wondering if there might be three states, where the third state is writable. > Air/brass would give very small differences in signal, I was thinking in that case it would be open/short circuit.