Todd Vierling wrote:
> 
> On Sat, 25 Apr 1998, Brian C. Grayson wrote:
> 
> :   Would a similar larger block size buy us as much
> : additional capacity from either ZIP disks or hard
> : drives?
> 
> No.  Zip disks and hard drives (basically one and the same with one
> removable and one not) give a sector-by-sector interface to the CPU, not a
> raw media interface where you can twiddle the format.  Additionally, the
> encoding of modern hard drives is no longer MFM, and is much more set in
> stone.

  The higher capacities I am discussing are independent of the
actual physical encoding method (MFM, FM, GCR, RLL), and would
benefit all such devices.  The savings are from converting
<header gap data gap>^n into header gap <data>^n gap, i.e., using
``useless'' dead/idle space for data, and not with changing the
lower-level bit format.

  To make a long story short, I did a little digging, and a
databook for the ST506 interface says the sector size can be
128, 256, 512, or 1024 bytes but no higher :(, so I think all
modern drives should support 1024.  The savings look like at
least 39 bytes saved per removed header&gap.  Plus, with larger
sectors, there'd be fewer interrupts etc.???  So it might be
worth investigating, once the floppy driver is done.  20MB
drives are pretty cheap nowadays, so it wouldn't be expensive
to play around without risking much...

  Brian
-- 
Brian Grayson (bgrayson@ece.utexas.edu)
Graduate Student, Electrical and Computer Engineering
The University of Texas at Austin
Office:  ENS 406       (512) 471-8011
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