Path: utzoo!attcan!uunet!portal!cup.portal.com!ts
From: ts@cup.portal.com (Tim W Smith)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Disk spunup/not mounting ?
Message-ID: <22450@cup.portal.com>
Date: 23 Sep 89 07:39:51 GMT
References: <4879@shlump.nac.dec.com>
Organization: The Portal System (TM)
Lines: 50

By the time the Mac gets around to running your INIT, it is too late.
The sequence at boot time is somethine like this ( for the exact
sequence, check the tech notes ):

	1. For each SCSI disk, load the driver for that disk

	2. Mount the disk that the System file is on

	3. Run INITs

	4. Most disk drivers loaded in step 1 have set the dNeedTime
	bit.  When they get called because of this, they post disk
	insertion events so that the Finder will mount their
	volumes

Since your disk has not yet been spun up by step 1, it's driver is
not loaded.  When you reboot, it has been spun up, so it then works.

This does not explain your report of it working sometimes the first
time.  Is it possible that it was already spun up from a previous
use?

Anyway, you will need to change your INIT to load the driver from the
disk after it spins up.  The information you need is in IM IV.  This is
what you have to do:

	1. Read block 0 of the disk.  This contains the Driver
	Descriptor Map.  This will tell you where the driver is
	on the disk.

	2. Allocate a non-relocatable block in the system heap big
	enough to hold the driver.

	3. Read the driver from the disk into this block.

	4. Read block 1 from the disk into another non-relocatable
	block in the system heap.

	5. Put the address of this block in A0, and put the SCSI id
	of the driver in D5.

	6. JSR to the start of the driver.  It will install itself
	and return to you.

You may want to change your INIT to check first to see if the driver
has already been installed, just for safety.  Do this by looking at
the entry in the unit table for your SCSI disk and seeing if it is
non-zero.  SCSI device N is supposed to use entry 32+N.

						Tim Smith