Date: Fri, 13 Aug 1999 18:39:51 +0200 (CEST) From: Wilko Bulte <wilko@yedi.iaf.nl> To: mwm@phone.net (Mike Meyer) Cc: freebsd-stable@FreeBSD.ORG Subject: Re: On freezes in 3.2-Stable Message-ID: <199908131639.SAA01361@yedi.iaf.nl> In-Reply-To: <Pine.BSF.4.10.9908122141570.94664-100000@guru.phone.net> from Mike Meyer at "Aug 12, 1999 9:45:55 pm"
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As Mike Meyer wrote ... > On Fri, 13 Aug 1999, W Gerald Hicks wrote: > :->When I kept up with the numbers for these things in a former > :->life working for a disk manufacturer, I was always astounded > :->at how much current the drives pulled during their power-on > :->sequence. After startup, current begins to taper off rapidly. > > This stopped being relevant a long time ago, but... > > DEC MIPS-based workstations worked around this problem by having > tweaked PROMs on their SCSI drives, with a SPIN-UP-ON-POWERON bit that > defaulted to off. Ultrix would send the drives the SCSI command to > spin them up - *after* everything else in the system was powered > on. This meant they could use a cheaper power supply, as no supported > configuration required it to deal with more than one drive spinning up > at a time. This applies to older DEC RZxx drives. The newer ones are set for staggered spinup which boils down to a delayed spinup after powerup with the delay being determined by the SCSI ID the drive is set to. So, something like: delay=3 seconds * SCSI ID This works just fine and helps a lot if you want to be easy on your PSUs. And for the record: it is no limited to MIPS Ultrix boxes, all DEC RZ drives had the wait for spinup command enabled. In some cases you can alter this behaviour by jumpering the drive, in other cases it is flipping a mode page bit. And it is not Ultrix sending the spinup command but the console code. Would be a bit difficult to boot a kernel from a disc waiting for a spinup command originating from the same kernel.. > Dealing with this was the *least* of the problems in trying to use DEC > SCSI drives on other platforms. But they could be made to work. What is so problematic about DEC scsi drives? You make me curious... Wilko -- | / o / / _ Arnhem, The Netherlands - Powered by FreeBSD - |/|/ / / /( (_) Bulte WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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