Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!spool.mu.edu!uunet!midway!quads.uchicago.edu!jcav
From: jcav@quads.uchicago.edu (john  cavallino)
Newsgroups: comp.sys.mac.hardware
Subject: Re: New SE/30 problem
Message-ID: <1991Jun7.013936.27592@midway.uchicago.edu>
Date: 7 Jun 91 01:39:36 GMT
References: <676094904.5@blkcat.FidoNet> <976@utsmips.csd.uts.EDU.AU>
Sender: news@midway.uchicago.edu (NewsMistress)
Distribution: comp
Organization: University of Chicago
Lines: 38

In article <976@utsmips.csd.uts.EDU.AU> james@uts.EDU.AU (J Boswell) writes:
>Bill.Whitacre@p916.f421.n109.z1.FidoNet.Org (Bill Whitacre) writes:
[stuff deleted]
>There is a strong possibility that the hard drive is not "ready" when the SCSI
>bus resets. I have had similar problems with an external drive taking too long
>and the internal drive booting when the external is the selected start up
>device.
>
>If this is the case and your HD is "missing the SCSI bus" then there are some
>ways around it if the mob who upgraded them cops out. Two possible H/W mods
>do effectively the same thing. i) mod the logic board so the reset pulse
>is longer (not recommended) or ii) put a delay on the 5 V line to the logic
>board so that the 12V is slightly ahead of it, giving the drive time to spin up.
>This one is not hard, a small inline inductor will work O.K.
>
>The third option is installing more memory thereby delaying the time when the
>Mac checks the SCSI bus to see who's available.
>
>The best option is of course to get the upgrader to supply a HD that is faster
>from power on to ready, usually the main factor is time to reach correct
>spindle speed.

!!!  Whoah!

There is a value stored in the PRAM of post-SE Macs that determines how long
the Mac will wait at startup for the hard disk to come up to speed.  There
are two Operating System calls for reading and setting this value, which
can be any number of seconds up to 31, with the default being 15.  Making a
quickie utility that sets this timeout value (I'm sure one already exists
somewhere) is much the best answer for disks that "miss the SCSI bus".
No hardware chopping required. :-)


-- 
John Cavallino                      |     EMail: jcav@midway.uchicago.edu
University of Chicago Hospitals     |    USMail: 5841 S. Maryland Ave, Box 145
Office of Facilities Management     |            Chicago, IL  60637
B0 f++ c+ g+ k s+(+) e+ h- pv (qv)  | Telephone: 312-702-6900