From: dlc@hpfcso.FC.HP.COM (Dennis Clark)
Newsgroups: comp.sys.mac.hardware
Subject: Re: SuperDrive heads, and why are they so expensive?
Date: 28 Sep 92 14:54:21 GMT
Organization: Hewlett-Packard, Fort Collins, CO, USA

In comp.sys.mac.hardware, berger@atropa (Mike Berger) writes:

> steggall@oski.berkeley.edu () writes:
> >Robert Wald writes:
> >_______
> >*   Exactly why are SuperDrives so expensive? They seem to be the
> >* same as PC drives (which I'm told can read Mac disks with the 
> >* proper software), only $220 (minimum for the Applied Engineering
> >* 1.44 drive) compared to $50 for a 1.44 PC drive. They eject 
> >* automatically, but what else is different? Is there any way 
> >* to fool a Mac into using a PC drive with the right cable and 
> >* manually ejecting at the right time?
> >________
> >From what I understand, Apple gets their drives from Sony. They
> >have a special contract with Sony to customize the drives to
> >Apple's specs. I don't know what they do to them that makes
> >them special, because it's possible to take non-Sony drives
> >and make them work with macs.
> *----
> According to Inside Macintosh, the Mac floppy drives use the 
> "IWM" custom interface (infernal woz machine?).  The sketchy
> details indicate that the drive interface is a little more
> primitive than a standard floppy drive, thus allowing you to
> use some of that extra CPU bandwidth to control the expensive
> floppy drive.

  I can't believe that someone hasn't posted the differences between PeeCee
type drives and Mac drives -- so in a nutshell this is it:

  A standard PeeCee 3 1/2" drive can't tell the computer that a disk is in
the drive, the Mac ones can. (They should be able to, but they don't seem to
use this feature in PeeCee drives.)  The value of this is that a disk can be
automounted by the OS without having to try to access the disk every so often.

  A standard PeeCee 3 1/2" drive can't eject a disk via computer control,
a Mac drive can.  The utility of this is rather obvious -- avoiding data 
corruption, and speeding backup/copy utility to name a couple.
 
  A Mac drive can change the spindle speed depending upon the track location
of the heads.  This increases the capacity of the drive and the reliability
of the data storage/retrieval.  The 1.44MB drives used in the Mac can do this
to read the lower density disks, but DO NOT do this on the 1.44MB disks -- 
this is why PeeCee's can read the 1.44MB disks that the Mac creates, and vice
versa.  It was wise for apple to avoid their propriatary encoding scheme on 
the higher density disks for interchangability of data with PeeCee's.

  So, the reasons for the higher cost of the Mac drives are two-fold and valid:
1.  They have more hardware in them, giving more functionality.

2.  They are a custom piece for a smaller market (Macs as opposed to PeeCee.)

  There are no dark designs, or secret plots that necessitate sarcastic 
cynicism -- except for Apple's tendency to overprice everything that they
sell anyway...

> --
> 	Mike Berger

DLC
-------------------------------------------------------------------------------
| Dennis Clark	(303)229-4313   telnet 1-229-4313  email dlc@fc.hp.com        |
| Hewlett Packard FWL Perf. Lab, 3404 East Harmony Rd. Ft. Collins CO 80525   |
-------------------------------------------------------------------------------