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From: lindhurs@schaefer.math.wisc.edu (Scott Lindhurst)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Both hard drives on to boot Mac Plus? (short summary)
Message-ID: <1991Mar28.213919.16619@schaefer.math.wisc.edu>
Date: 28 Mar 91 21:39:19 GMT
References: <1991Mar27.050325.3851@schaefer.math.wisc.edu>
Reply-To: lindhurs@schaefer.UUCP (Scott Lindhurst)
Organization: Univ. of Wisconsin Dept. of Mathematics
Lines: 21

In article <1991Mar27.050325.3851@schaefer.math.wisc.edu> I write 
>I just connected two hard drives to my Mac Plus, and now I can't
>boot from one until they are both turned on.

From the responses so far, I think that the answer
in my case is probably that the SCSI specifications
say that all SCSI devices must be powered up for everything to
work; older devices may do things that require them to be on
(such as not providing termination or clamping lines to ground
when they are off), but newer devices are usually friendlier
and the SCSI bus will work with them on or off.

The only real solutions seem to be to disconnect the older drive
when I'm not using it or maybe use an external terminator
instead of the internal.

If anyone is interested in the detailed responses, let me know
and I'll send a copy.

Scott Lindhurst
lindhurs@math.wisc.edu