Date: Thu, 14 Dec 1995 17:21:10 +0000 () From: Michael Smith <msmith@atrad.adelaide.edu.au> To: scrappy@hub.org (Marc G. Fournier) Cc: msmith@atrad.adelaide.edu.au, ejc@gargoyle.bazzle.net, questions@FreeBSD.ORG Subject: Re: ACER Motherboard: SCSI Recommendations? Message-ID: <199512141721.DAA25793@genesis.atrad.adelaide.edu.au> In-Reply-To: <Pine.BSF.3.91.951214012610.3868C-100000@hub.org> from "Marc G. Fournier" at Dec 14, 95 01:30:41 am
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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." [[
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