From owner-freebsd-questions Wed Dec 13 22:42:12 1995 Return-Path: owner-questions Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id WAA10706 for questions-outgoing; Wed, 13 Dec 1995 22:42:12 -0800 (PST) Received: from genesis.atrad.adelaide.edu.au (genesis.atrad.adelaide.edu.au [129.127.96.120]) by freefall.freebsd.org (8.7.3/8.7.3) with ESMTP id WAA10692 for ; Wed, 13 Dec 1995 22:42:01 -0800 (PST) Received: from msmith@localhost by genesis.atrad.adelaide.edu.au (8.6.12/8.6.9) id DAA25793; Fri, 15 Dec 1995 03:51:10 +1030 From: Michael Smith Message-Id: <199512141721.DAA25793@genesis.atrad.adelaide.edu.au> Subject: Re: ACER Motherboard: SCSI Recommendations? To: scrappy@hub.org (Marc G. Fournier) Date: Thu, 14 Dec 1995 17:21:10 +0000 () Cc: msmith@atrad.adelaide.edu.au, ejc@gargoyle.bazzle.net, questions@FreeBSD.ORG In-Reply-To: from "Marc G. Fournier" at Dec 14, 95 01:30:41 am MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-questions@FreeBSD.ORG Precedence: bulk Marc G. Fournier stands accused of saying: >> "Fast" is a prerequisite for any new disk; "wide" means the controller >> has the extra bits required to talk to a "wide" SCSI device, should you >> wish to connect one. >> > What does "wide" give? Increased communications speed to the drives? > Less bus lag/contention? 16-bit databus v. 8-bit databus. Double bandwidth, but a bigger cable. >> If you want to look at one to verify this for yourself, the little resistor >> packs should have '111' on them, but _not_ "221331" or "220/330" or similar. >> > And todays trick question...what do they mean? '111' are the 110 ohm resistors to a 2.9V regulated supply for active termination. 220/330 or 221331 are the dual-resistor networks for passive termination (220 ohms to +5, 330 ohms to ground). Passive networks don't provide particularly good termination in the case of the fast signal edges that you see on a fast SCSI bus. If you want to know more, look up "Thevenin" in any halfway decent electronics textbook. > Marc G. Fournier | POP Mail Telnet Acct DNS Hosting -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 041-122-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] "Who does BSD?" "We do Chucky, we do." [[