From owner-aic7xxx Thu Sep 30 1:38:32 1999 Delivered-To: aic7xxx@freebsd.org Received: from enkur.wsr.ac.at (enkur.wsr.ac.at [143.130.50.57]) by hub.freebsd.org (Postfix) with ESMTP id BE3F015110 for ; Thu, 30 Sep 1999 01:38:21 -0700 (PDT) (envelope-from hjp@enkur.wsr.ac.at) Received: (from hjp@localhost) by enkur.wsr.ac.at (8.9.3/8.9.3) id KAA04096 for aic7xxx@FreeBSD.ORG; Thu, 30 Sep 1999 10:38:17 +0200 Date: Thu, 30 Sep 1999 10:38:17 +0200 From: "Peter J. Holzer" To: aic7xxx@FreeBSD.ORG Subject: Re: fast drives. Message-ID: <19990930103817.Q1137@wsr.ac.at> Mail-Followup-To: aic7xxx@FreeBSD.ORG References: <19990929093341.C4929@elmo.cygnus.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="jsrFa/5v3cIbBmG8"; micalg=pgp-md5; protocol="application/pgp-signature" X-Mailer: Mutt 0.95.3i In-Reply-To: ; from Gregory Hosler on Thu, Sep 30, 1999 at 03:25:27PM +0800 Sender: owner-aic7xxx@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org --jsrFa/5v3cIbBmG8 Content-Type: text/plain; charset=us-ascii On 1999-09-30 15:25:27 +0800, Gregory Hosler wrote: > Ignorant question time. What's "SE" ?) SE means "single ended". There is a single wire for every signal. The normal SCSI bus (and all devices attached to it) uses this scheme. There are also "differential" busses, where two wires are used for every signal - one with a positive voltage, one with negative. This allows for longer cabling at the same speed (or higher speed at the same length) and has mostly been used for attaching external disk arrays until recently (For fast ethernet you can use cables up to 25 meters with this scheme). For Ultra2 speeds, an SE bus would have become too short and sensitive even for PCs, so they use a differential scheme, but with a lower voltage, so there are now three electrically incompatible schemes: SE, differential, and LVD. hp -- _ | Peter J. Holzer | Nobody should ever have to be |_|_) | Sysadmin WSR / Obmann LUGA | ashamed if they have a secret love | | | hjp@wsr.ac.at | for writing computer programs that __/ | http://wsrx.wsr.ac.at/~hjp/ | actually work. -- Donald E. Knuth --jsrFa/5v3cIbBmG8 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia iQDQAwUBN/MheFLjemazOuKpAQGeigXUDJcxZef8ducS2nPa2l1r3PRhpDBVpb7g zaFt6ipJVqMGYxV79cBLmdNIX11jRFu2Apkoymx/7rYptbmVaIFGEWzsny3TsckV LmpZsmDy4JCUicqY8TDoS2NTbj0vrG2EeX5870lWXBfopbaJxIvRH0Lq0DE3xxxI v26fVywHmI9x6/SXe62q1xquE5nzZWzA43EPDRBoO8IWq+/CAEhnGMNKdA7C96PW i576R8mct1W0FKoNgTNYmFotxA== =L/oB -----END PGP SIGNATURE----- --jsrFa/5v3cIbBmG8-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe aic7xxx" in the body of the message