AUTOPARK -- a routine to park the fixed disk heads when the disks
are not in use.

One soon learns, after installing hard disks on a PC (or, at any rate,
after READING about hard disks), that they are sensitive to vibration.

Staggering into the table on which a hard-disk-equipped PC is running
can jar the disk sufficiently to damage information stored on the
disk. Even when the PC is turned off, IBM recommends that the heads
of the hard disks be parked before moving the PC.

IBM provides a method of doing this, but only on the DIAGNOSTICS
diskette. I found this inconvenient.

AUTOPARK is executed only once, preferably in the AUTOEXEC.BAT at
system startup. For each of the two hard disks that you may have
on your system, it does the following:

1 Determines whether that hard disk is present.

2 By trying each cylinder in turn, determines the highest-
numbered cylinder to which the disk can seek. This is
the cylinder reserved as a PARKing place. The first
version of AUTOPARK did this one cylinder at a time,
starting at cylinder 0. The present version first does
it 100 cylinders at a time, then 10 cylinders at a time,
and finally one cylinder at a time. On a Seagate 225
hard disk, this reduced the time from perhaps half a
minute per drive to perhaps half a second.

3 Parks the head at that cylinder (it may be different for
the two drives if both are present; some people have
dissimilar drives -- for example, a 10 megabyte drive
and a 20 megabyte drive).

4 Terminates and remains resident and thereafter rePARKS
the heads any time they have not been used for 30 seconds.

Thirty seconds seemed reasonable to me; but you can change it easily
by examining the source and changing one constant.

The files supplied are: AUTOPARK.DOC this DOC file
AUTOPARK.ASM assembler source code
AUTOPARK.COM the executable module,
obtained by processing
AUTOPARK.ASM with the programs
MASM, LINK, and EXE2BIN.

Carl Hayes (SYSOP, NN5I BBS, 214-960-2730)