MFMulation? (Solid-state replacements for MFM drives) - test-drb@ccmp.vtda.org

16 Apr 2007

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Subject: Re: MFMulation? (Solid-state replacements for MFM drives)
   From: "Ethan Dicks" <ethan.dicks at gmail.com>
   Date: Sun, 15 Apr 2007 21:22:33 -0500
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

On 4/15/07, Roger Merchberger <zmerch-cctalk at 30below.com> wrote:
  Ah, but the beauty of this is, if you make it IDE
compatible, you already
 *have* flash compatibility - just slap a CompactFlash module of your
 preferred size into a CF->IDE adapter, and Bob's your uncle! 
Since desktop drives are moving to SATA, compatibility with PATA (and
thus easily attached Compact Flash drives) isn't the obvious goal is
once was.  Yes, there will be large amounts of PATA drives for a
number of years, but I can see that in a small number of years, they
just won't bother to make them anymore, whereas, Compact Flash is
Compact Flash - they may stop making that, too, but they aren't as
mechanically fragile, so they may be easier to track down 10+ years in
the future.

  I doubt there were MFM drives (read: ST506)
available that hit the
 gigglebyte size 
There's an understatement - with a practical maximum number of
platters and heads and tracks and sectors with the techniques of the
times, no... they never got close to 1GB.  They came out at 5MB
(ST506) and peaked under 200MB.  ESDI was the interface of choice for
a short time if you wanted "large" drives on the desktop, then IDE
(PATA) swept in and here it is, sweeping back out like the tide.  As
an aside, I happen to have a pair of 600MB ESDI drives on an SDI
controller on my VAX8200, so ESDI isn't just for large PCs, but they
were seen there. 
What made the jump possible was RLL.  MFM drives could do RLL and 
those Xt2190 (153mb) drives now exceeded 200mb and climbing.

IDE was simple pushing the RLL controller onto the literal back of 
the drive making the path clear for yet higher data rates to the platter.
Cobalt replaced ferrite for the surface media, data rates went up.
Better heads, amps and the like made even higher data rates possible 
so that 1Gb and higher was possible.  By then GCR and other techniques
were being applied to the problem of getting more into less.

MFM was a starting point and had limited use because it didn't pack the 
maximum number of bits possible.  

Allison