Date: Thu, 31 Oct 1996 22:38:38 +0100 (MET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: imp@village.org (Warner Losh) Cc: rgrimes@GndRsh.aac.dev.com, lada@ws2301.gud.siemens.co.at, scsi@freebsd.org Subject: Re: FreeBSD support for Adaptec/Buslogic drivers Message-ID: <199610312138.WAA02295@yedi.iaf.nl> In-Reply-To: <E0vJ0WE-0001Qi-00@rover.village.org> from "Warner Losh" at Oct 31, 96 10:03:02 am
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As Warner Losh wrote... > > In message <199610311654.IAA04790@GndRsh.aac.dev.com> "Rodney > W. Grimes" writes: > : They are not all equal, the ``cheap'' ones use passive termination, > : the good ones (ASUS SC-200 and many others) use active termination. > > That brings up a question that I've been meaning to ask for a long > time. Can someone tell me the difference between active and passive > termination, or point me at something that does? In addition, why > would I want one over the other? The faster and or longer the bus, the more you want active terminators. Passive terminators are not more that a pair of resistors, one connected to +5V (TERMPOWER), the other connected to ground. The 2 other ends of the resistors hookup to eachother and the SCSI bus line. Active terminators come in different incarnations, you even have completely silicon (chip) variants. The idea is that they contain more or less elaborate electronics (clamp diodes, voltage regulators etc) that give a cleaner bus signal, reducing under/overshoot etc. Wilko _ ____________________________________________________________________ | / o / / _ Bulte email: wilko@yedi.iaf.nl - Arnhem, The Netherlands |/|/ / / /( (_) Do, or do not. There is no 'try' - Yoda --------------------------------------------------------------------------
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