Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!crdgw1!crdos1!davidsen
From: davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr)
Newsgroups: comp.sys.ibm.pc
Subject: Re: AT vs ST506 Interfaces
Summary: ST412
Message-ID: <962@crdos1.crd.ge.COM>
Date: 10 Oct 89 14:30:13 GMT
References: <1989Oct4.234853.20690@mccc.uucp>
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Distribution: na
Organization: GE Corp R&D Center
Lines: 22

In article <1989Oct4.234853.20690@mccc.uucp>, pjh@mccc.uucp (Pete Holsberg) writes:
|  I saw an Imprimis ad recently that hawked their WREN line of hard disks.  They
|  listed interfaces as ST506, AT, ESDI, and SCSI.  I'm familiar with ST506, ESDI
|  and SCSI, but what do they mean by AT?  I thought that a HD with an ST506
|  interface could be used with an ST506 controller on an XT or AT or even an
|  AT&T 3B2/400.  How does an AT interface HD differ from an ST506 device?

  An AT does not have an ST506 interface, it has an ST412 (often called
AT) interface. The diference is that the 412 offers "buffered seek." On
the 506, to step 20 tracks the controller does a "step...wait" 20 times,
while on the 412 the controller sends 20 step commands then a wait. The
next effect is that the seek is faster since the head doesn't stop at
each track. An AT drive will work on an ST506 controller, since it's a
superset. The other way round may result in seek errors.

  This info taken from a Seagate tech note supplied by IBM when the
first AT's came out.
-- 
bill davidsen	(davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen)
"The world is filled with fools. They blindly follow their so-called
'reason' in the face of the church and common sense. Any fool can see
that the world is flat!" - anon