Date: Wed, 19 Feb 1997 19:40:09 +0100 (MET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: gilbertd@cs.man.ac.uk (David Alan Gilbert) Cc: dufault@hda.com, scsi@freebsd.org Subject: Re: About to go SCSI - advice? Message-ID: <199702191840.TAA00702@yedi.iaf.nl> In-Reply-To: <9702191255.AA22930@amu7.cs.man.ac.uk> from "David Alan Gilbert" at Feb 19, 97 12:55:58 pm
next in thread | previous in thread | raw e-mail | index | archive | help
As David Alan Gilbert wrote... > > Peter spoke thus: > > > No, Joerg. Any device that can become an initiator must supply > > terminator power (so Simon must have more than one device with > > TERMPWR to meet the letter of the spec). Other devices can as long > > as they don't exceed the total maximum current (which is huge - I > > think it is something like 5 amps and is driven by regulatory This highly depends on what you use for the SCSI bus. I've seen eh hum interesting things happen with 6 SCSI devices all feeding TERMPWR to a single printed circuit backplane that got shorted. All devices are fused with 1 or 1.5 Amps. Printed wiring does not like that (and most likely ribbon cable also has problems). > > My intuitive opinion is that the host adapter and the devices at > > either end of the chain should provide TERMPWR. > > Our problem originally started when we found a device which wouldn't > work (at all - wouldn't even respond to identify) unless it had Some harddrives need termpower to start spinning. > termpwr when it was switched on; so you had to switch the source of > termpwr on first and then the drive. > > 50% of the SCSI users in the world say you should have 1 term power device, At least one, being the initiator as per SCSI-2 standard. > 50% of the SCSI users say that you can have as many as you like, > and the other 80% say termpwr - what? See the shorting issue. > To make life bareable we turned termpwr on on that drive enabling it to > be switched on; but the docs with our Adaptec don't say >ANYTHING< > about termpower - they don't say where the fuse is, how to turn it on/off, > whether it should be on/off etc. Newer cards tend to have self-restoring fuses. Look for small obscure metal thingy (approx 0.4" square). That might be it. Wilko _ ____________________________________________________________________ | / o / / _ Bulte email: wilko@yedi.iaf.nl - Arnhem, The Netherlands |/|/ / / /( (_) Do, or do not. There is no 'try' - Yoda --------------------------------------------------------------------------
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199702191840.TAA00702>