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Path: utzoo!attcan!telly!eci386!clewis
From: clewis@eci386.uucp (Chris Lewis)
Newsgroups: comp.sys.att,unix-pc.general
Subject: Re: wanted: info on Micropolis 1355
Keywords: disk micropolis
Message-ID: <1989Jul28.143850.16747@eci386.uucp>
Date: 28 Jul 89 14:38:50 GMT
References: <254@gnosys.UUCP>
Reply-To: clewis@eci386.UUCP (Chris Lewis)
Distribution: na
Organization: R. H. Lathwell Associates: Elegant Communications, Inc.
Lines: 37

In article <254@gnosys.UUCP> gst@gnosys.UUCP (Gary S. Trujillo) writes:
>I recently discovered a Boston-area source (which does mail-order) for
>the Micropolis model 1355, which has a formatted capacity of 159 Mbytes
>(it's 170 Mbytes unformatted).  The drive has eight heads with 1024
>cylinders, so I'm assuming it wouldn't require the P5.1 upgrade, though
>it would need the WD2010 chip (right?).

What it needs is an ESDI controller.  The Micropolis 1355 has an ESDI
interface, the WD2010 (and supportable 3b1 drives) are ST506.

>Anyway - does anyone know whether this drive could be used with the 3B1?

Not unless somebody's selling an ESDI controller for the 3b1.

Rule of thumb: 5.25" ST506 drives have 8 1K or 17 512 byte sectors per track
(yeah, some controllers are one more or less).  Eg: roughly 8-9K per
track.  Multiply by # heads and # cylinders.  The reason why I caught
this one is that 8 heads and 1024 cylinders would be an 85 Mb drive
in normal situations (eg: Maxtor XT1085, Micropolis 1325 or Miniscribe
6085).  Since it had *twice* the storage that it should have for it's
geometry, it had to be something other than ST506/MFM - ESDI usually averages
34 512 byte sectors/track.  If it had been only %50 larger, I would have
suspected RLL - which isn't available for 3b1s either.

I believe that the max fully legal (w.r.t. the ST506 interface
standard) size for a ST506 is 15 heads and 1024 cylinders, which works
out to about 140Mb unformatted.  For that you need the WD2010.

In the case of IBM AT style machines, it is possible to obtain controllers
that play tricks with ESDI or SCSI drives to make them look like monster
ST506's (eg: the 64 sector/track fudge in Adaptecs and WD1007s), but,
sorry, nobody's got 'em for 3b1s as far as I know.
-- 
Chris Lewis, R.H. Lathwell & Associates: Elegant Communications Inc.
UUCP: {uunet!mnetor, utcsri!utzoo}!lsuc!eci386!clewis
Phone: (416)-595-5425