[comp.sys.mac.programmer] CD SCSI w/o Multifinder - Why?!

pff@thumper.bellcore.com (Peter Ferris) (02/02/89)

Does anyone know why Apple's CD ROM (SCSI) won't permit the use of 
multifinder when playing an audio CD?  Was this a "hurry up an get it to 
market" approach, or is there a technical reason for this.  If there is a
technical problem, can it be overcome in future software / upgrades, etc; or
am I destined to run "singlefinder" forever if I want to listen to a CD?

If memory serves, I can run multifinder for "normal" use of the CD ROM drive.
Please e-mail any responses to me.  I can't check this group as often as I'd
like to.

Thanks for your help,

Pete Ferris
pff@thumper.bellcore.com

blob@Apple.COM (Brian Bechtel) (02/02/89)

In article <1454@thumper.bellcore.com> pff@thumper.bellcore.com (Peter Ferris) writes:
>Does anyone know why Apple's CD ROM (SCSI) won't permit the use of 
>multifinder when playing an audio CD?  

The AppleCD SC drive works fine under Multifinder.  The CD Remote desk
accessory plays audio CDs just as you would expect it to play them.

You haven't described what problem you are having.  I can imagine one
scenario where you might run into problems with audio CDs.  If you
installed only part of the new software release, you would get
unexpected results.  The full explanation follows:

When the AppleCD SC drive was first shipped, the High Sierra/ISO 9660
software wasn't ready.  Early purchasers of the drive received a coupon
in the box which, if sent in, gave you a software update plus the Apple
CD-ROM Explorer disc, a demonstration CD that is now part of every
AppleCD SC shipped.

The original (1.0) driver software checked any CD inserted to see if it
was HFS.  If the disk was not HFS (audio, High Sierra, ISO 9660, or
anything else) then a disk-inserted event was never posted.  This meant
that audio disks never showed up in the Finder.  This had to be
implemented this way, since we had no external file system that could
support audio CDs.

The High Sierra/ISO 9660 software is implemented as an external file
system (for sparse details, see Inside Macintosh, which basically 
describes an external file systems hook without documenting it.)  In
order to be able to mount High Sierra/ISO 9660 CDs, we needed to always
get a disk-inserted event.  The driver was modified to remove the check
for HFS, and we wound up with three file system translators working
under the external file systems hook, all controlled by an INIT called
Foreign File Access:
	1) High Sierra file access
	2) ISO 9660 file access
	3) Audio CD access
Again, we had to remove the check in the driver, or we wouldn't be able
to support ISO 9660 and High Sierra CD-ROMs.

The file "Audio CD access" provides the minimum support necessary to
allow audio CDs to be mounted under the Finder.   Tracks show up as
"files" of length 0, type 'trak', creator 'aucd'.  If you do a "Get
Info" on a track, you find the time of the track in the comment field.
If you do a "Get Info" on the disk, you find the total time of the CD
in the comment field.

This means that there are now seven pieces of software which are
part of the release, rather than three.
	Apple CD-ROM				(updated in the new release)
	CD Remote Init				(updated in the new release)
	CD Remote desk accessory	(updated in the new release)
	Foreign File Access			(new)
	High Sierra File Access		(new)
	ISO 9660 File Access		(new)
	Audio CD Access				(new)
Now, if you used the installer & Font/DA Mover supplied on the
Macintosh CD Setup disk to install the new pieces, everything was
installed properly.  All the installer does is drag these pieces into
your System Folder.

*If* you just dragged over a new Apple CD-ROM without dragging over at
least Foreign File Access and Audio CD Access, then the system will
attempt to mount the audio CD, find that it isn't HFS, find that there
is no external file system to handle the audio CD, and give you the
alert "This is not a Macintosh disk."

Now, after saying all this, if you still have a problem, you should
describe the problem ("it doesn't work" isn't a description of the
problem) and I'll be happy to try and figure out what's happening.

--Brian Bechtel		blob@apple.com
AppleCD SC and CD ROM Explorer are trademarks of Apple Computer, Inc.
I wrote the High Sierra and ISO 9660 file system translators, and was
software lead on the second revision of the software.  This stuff all
works, really, it does.  I use it every day.