Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!ukma!kherron
From: kherron@ms.uky.edu (Kenneth Herron)
Newsgroups: comp.sys.amiga.programmer
Subject: Speeding up floppy disk heads
Message-ID: <1991Jun8.001706.13497@ms.uky.edu>
Date: 8 Jun 91 00:17:06 GMT
Distribution: na
Organization: University Of Kentucky, Dept. of Math Sciences
Lines: 26

Over in .applications someone asked about a program called speedup which
changes the head step rate on floppy drives.  I did a rewrite of this
program some time ago and (having been reminded) am wondering about
something.

The program modifies a longword 11 bytes from the beginning of the
device's trackdisk unit record; this is a private area beyond the end
of the TDUPublicUnit structure.  The TDUPublicUnit structure also
contains two longwords for the step delay and head settle time, but
while I was hacking these fields always contained large negative numbers
(or something large anyway, I don't recall exactly).  Clearly these
fields don't contain the step and settle delays, so how are they used?
And what value is actually stored at the 11th longword?

No flames about modifying private data please; I can't find *any* 
documentation about the public fields and I never released the thing 
anyway.

FYI:  I can change the step(?) delay from 3000 ms down to 1900 ms without
problems; around 1800 it gets unreliable.  The biggest benefit is that
the drives make less noise.
-- 
Kenneth Herron                                            kherron@ms.uky.edu
University of Kentucky                                       +1 606 257 2975
Department of Mathematics       "So this won't be a total loss, can you make
         it so guys get to throw their mothers-in-law in?"  "Sure, why not?"