Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!caip!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!inuxc!inuxh!rdr
From: rdr@inuxh.UUCP (Robert Rindfuss)
Newsgroups: net.micro.pc
Subject: Re: "AT" Hard Disks
Message-ID: <470@inuxh.UUCP>
Date: Sun, 31-Aug-86 23:16:42 EDT
Article-I.D.: inuxh.470
Posted: Sun Aug 31 23:16:42 1986
Date-Received: Mon, 1-Sep-86 18:55:19 EDT
References: <465@newton.physics.purdue.edu.ARPA>
Distribution: net
Organization: AT&T Consumer Products, Indianapolis
Lines: 37

> I am considering the purchase of a hard disk to replace the 10 meg'er in
> my pc look-alike.  I am intrigued by the disks advertised as for the 
> "AT".  Are these disks ST-506 compatible?  Is the transfer rate
> (as opposed to the step rate) the same as disks for "XT" systems?
> I am particularly interested in the 30 meg CMI disk advertised for
> about $350.  Any known problems with this disk?
> 
This has come up before, so I thought I'd post a reply.

The only significant difference between the ST506 (used in XTs) and the
ST412 (used in AT) drives has to do with track seeking - the 412 generally
is a more intelligent drive, and is capable of doing "buffered seeks."
This means the controller can blast a series of step pulses to the drive
at a very fast rate, and the drive will buffer these, then move the heads
in one operation to the desired track, rather than stopping to settle on
each intermediate track. The good news for you is that any ST412 drive
will work with an ST506 controller, as far as seeks are concerned.  The
worst that will happen is that the controller will not seek tracks as
quickly as the drive might be capable of.  The one thing to be sure first
is that you can set your controller to handle the drive's number of
heads and cylinders; the CMI 30meg has 6 heads and 640 cylinders.

As for the CMI drives, I once put one of these on an AT&T 6300 using a
DTC5150 controller - it worked just fine.  It was one of the quietest
drives I've ever (not) heard.  I later returned the drive after getting
cold feet about a drive from a company no longer in the drive business.
But I think it was probably a good drive (not to be confused with the
CMI 20meg drives of such notoriety in the IBM ATs, which had a different
servo design.)

By the way, I got it from a place called PC Systems in W. Palm Beach FL
(305) 863-8447 for $279.  Same drive BCE is selling for $350.  I had
a good experience with them, both buying the drive and later returning it.

Bob Rindfuss
AT&T Consumer Products, Indianapolis
...ihnp4!inuxh!rdr