non-SCSI disks on a SCSI disk interface (was Re: Space, the next frontier) - test-drb@ccmp.vtda.org

26 May 1999

I don't think they could be extended to 4K cylinders either.  1224 x 15 was
a pretty common geometry.  It even appeared in some BIOS drive tables.  The
4380E was built like that wasn't it?  Most manufacturers had an ST-506
interfaced drive with the same geometry as their ESDI drives so they had
someplace to put the platters/HDA's which didn't handle the servo well
enough.  One surface was dedicated for servo, IIRC.

The 4380 was about 1224x15x35 or 36 (take your pick, and set the jumper).
The WD1007 ESDI controllers would make that look like 636x16x63 or some
such.  You didn't have to sacrifice capacity in order to use that.  It was
their RLL and MFM controllers that couldn't translate track/sector
geometries.

Dick

-----Original Message-----
From: Don Maslin &lt;donm(a)cts.com&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Wednesday, May 26, 1999 10:57 PM
Subject: Re: non-SCSI disks on a SCSI disk interface (was Re: Space, the
next frontier)

...
 On Wed, 26 May 1999, Allison J Parent wrote:

> <Someone should correct me if I'm wrong (I'd be interested in knowing
that
...
 > <I'm wrong!), but the largest capacity MFM
geometry is that of the Maxtor
> <XT2190 (1024 cylinders * 15 heads), giving you just under 150 Mbytes
(M=10*
...
 > <after formatting at 19 sectors/track.  And the
RLL version gets
> <another 30% or so of capacity.
>
> The 2190 is 1224*15.  However the number of cylinders can be increased (it
...
   was controller
limit not the drive)  the limit, I think is closer to
 4096*16*18*512 or roughly over 600mb.  The problem is that RLL with the 
Do you mean that Maxtor used only about the first third of the available
platter for data?  That seems like a bit of a waste.  I do recall - years
back - discussion about how the XT1085 could be extended, but not by a
factor of three!
 - don

> higher bit packing, and EDSI with the higher data rates put more data on
> a square inch of media and make more sense than pushing the mechanics of
> the drive.
>
> <Of course, large embedded-controller SCSI drives are readily available on
t
...
   <surplus
market these days.  9 Gbyte drives start below $150.00, and
 <2 Gbyte drives seem to get around $40.

 And they are small too!

 Allison