Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!isis!ico!rcd
From: rcd@ico.isc.com (Dick Dunn)
Newsgroups: comp.unix.i386
Subject: Re: < 3 SCSI Drives on ISC 2.02 (problem) >
Summary: power sequencing
Message-ID: <1990Aug6.200618.16262@ico.isc.com>
Date: 6 Aug 90 20:06:18 GMT
References: <675@unlisys.UUCP> <3491@tmiuv0.uucp> <11090@alice.UUCP> <1990Aug03.132554.13326@scuzzy.mbx.sub.org>
Organization: Interactive Systems Corporation, Boulder, CO
Lines: 21

src@scuzzy.mbx.sub.org (Heiko Blume) writes:
...debra@alice.UUCP (Paul De Bra) writes:
> >There is a potential problem indeed, but what's most important is how
> >power hungry the drives are...
...
> the danger is how much the drives need when you power them up. i RTFM'ed
> a bit and found out that my 600MB WREN V uses up to 4.5 ampere on startup
> (on 12V)...

Blume's point is a good one: the limiting factor for powering the drives is
almost certainly the startup power.  It's time to re-invent something else
the mainframe world has known for a long time:  power sequencing.

One of the folks here has a box'o'disks (SCSI) which are designed to power-
sequence themselves.  The idea is very simple:  Each drive delays its spin-
up from the time it gets logic power by an interval directly related to the
drive's SCSI ID.  Seems simple and eminently sensible.  (How common is
this, anyway?)
-- 
Dick Dunn     rcd@ico.isc.com -or- ico!rcd       Boulder, CO   (303)449-2870
   ...Are you making this up as you go along?