Subj:   Disc Wear Check prog (Sam)

Dear fellow CHHUers,

Below is a '71 BASIC program which I originaly intended to send to several
people on disc, but thought everyone might be happier to see the program
uploaded here on this BBS.  It reads the HP Media Monitor information on
a 3.5" disc inserted into an HP9114A/B disc drive.  The report contains
both the actual "wear count", which is the total number of head-loaded 
revolutions the disc has gone through, and an estimated % usage, with
100% being 1114112 revolutions.  The wear count is read every time a new
disc is inserted.  In a quiet room you can hear the drive head buzz all the
way to the innermost track and back.  HP disc drives update the wear count
on the disc only every 1024 head-loaded revolutions.  If the disc is
ejected before this occurs, the count will not get a chance to be updated.
This means that frequent disc ejects will make the medium wear info
inaccurate and therefore misleading.

Also, since a 3.5" disc spins 10 times a second in the drive, this means
the wear count info will need updating as little as 100 seconds after
the previous update.  This also explains why sometimes the head decides to
move out of its way to the innermost track and back before resuming its
original task.  Newly initialized discs will always have E60000 (HEX), meaning
0% usage.  That's why discs should not be re-initialized or else the medium
wear count will be reset.  When the count reaches F70000 (HEX), most HP
drives will either blink the disc access light or click the head to warn
the user of the disc getting worn out.  At this point, the wear percentage
is 100%.  If accesses are continued and the count reaches a second wear
level of FE0000 (HEX), or about 1.57 million revolutions, then the drive
will automatically write-protect the disc.

Should the wear count reach a third level wear constant (FF0000 -->
1.64 million revs), then most HP disc drives will refuse to read the disc.
All data on the disc is thus lost!  But hopefully, the contents will have
been backed up on a good disc.

The program does not work on single-sided discs, or double-sided discs
initialized in single-sided format.  In this format there appears to be no
wear count maintained.  Also discs formatted into 1 Kbyte sectors (if you
know how) will not work properly with the program.  HP MS-DOS format
(for the Portable/PPLUS) and HP LIF format (for HP-41/71/75/85/9836....)
discs are, however, correctly handled.

If you encounter a problem, first check that you have the exact sequence
of DATA bytes in the long, fragmented SEND statement (especially if you
are typing the code in).  Also, the program was only debugged using a
HP9114B drive and an HP9114A drive with Rev. D firmware EPROM (09114-15516)
installed.  For 9114A's with earlier firmware revisions, the program may
error out.  Please send me feedback if this happens.

Enjoy!
                                                     Sam Chau   [242]   8-)