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From: bates@ssdevo.dec.com (Ken Bates	DTN 522-2039)
Newsgroups: net.micro.mac
Subject: Question on contents of \"BootDrive\"
Message-ID: <5950@decwrl.DEC.COM>
Date: Tue, 14-Oct-86 11:41:05 EDT
Article-I.D.: decwrl.5950
Posted: Tue Oct 14 11:41:05 1986
Date-Received: Mon, 20-Oct-86 14:52:35 EDT
Sender: daemon@decwrl.DEC.COM
Organization: Digital Equipment Corporation
Lines: 16


Does anyone know if the global location "BootDrive" (location 0x210) is 
really valid? If I access it on either a HD20 or a HyperDrive, the contents 
are 0x8023, which strikes me as a rather weird drive number. If I take this 
number as valid and skim through the vcb queue looking for a match, I never 
find it (looking for a match between BootDrive and vcbDrvNum). Booting from 
a floppy, BootDrive turns out to be 0xFFFF, which is even stranger.

The goal of this was to find out the vRefNum of the boot drive (i.e., which
drive should not be unmounted). I had planned to access BootDrive, then skim
through the vcb queue looking for a match, and then using vcbVRefNum of the
matching vcb entry, but since the contents of BootDrive appear to be bogus,
I can't do it this way. Any suggestions on 1) why this fails and 2) how to
determine the boot drive?

 - Ken Bates