Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!spool2.mu.edu!uunet!mcsun!unido!ira.uka.de!fauern!opal!tmpmbx!scuzzy!src From: src@scuzzy.in-berlin.de (Heiko Blume) Newsgroups: comp.periphs.scsi Subject: Re: SCSI max length Message-ID: <1991Jan06.000325.22323@scuzzy.in-berlin.de> Date: 6 Jan 91 00:03:25 GMT References: <37560@cup.portal.com> <1991Jan04.191812.16844@scuzzy.in-berlin.de> Organization: Contributed Software Lines: 34 urlichs@smurf.sub.org (Matthias Urlichs) writes: >In comp.periphs.scsi, article <1991Jan04.191812.16844@scuzzy.in-berlin.de>, >< tho, i'm not sure about the max length with this, if the adapters >< don't have their own power supply. >< >If not, the adapter should have a standard power connector, just like the >SCSI drives you're connecting to it. >Powering anything bigger than a terminator pack off the SCSI bus probably is >not a good idea. that's what i meant by 'own power supply', that they do *not* get it from the cable.. >< the optimum cables are: >< - 132 ohms imp. 50 cond. flat or 25 signal twisted pair cable for Single Ended >< - 122 ohms imp. 50 cond. or 25 signal twisted pair cable for Differential >The ohms may be important depending on how sensitive/fast your devices are. >If there is a mismatch there can be echoes from the terminators, which can >disrupt bus communications. yep, tho the above numbers are what the standard (17b) recommends. however since it might be difficult to obtain such cables, it says lower impedance might work too. if i were to use a 20m cable i'd really try hard to get the optimum material, tho :-) what kind of adapters do you use anyway?? -- Heiko Blume <-+-> src@scuzzy.in-berlin.de <-+-> (+49 30) 691 88 93 public source archive [HST V.42bis]: scuzzy Any ACU,f 38400 6919520 gin:--gin: nuucp sword: nuucp uucp scuzzy!/src/README /your/home