article 11321 in comp.sys.amiga
Subject: noKLICKstart (V1.0c)
Summary: Peace,quiet, and empty drives
Keywords: Kickstart, patch, WCS, click, trackdisk.device
Organization: Tubualar Transport, Inc.


Empty drives on the Amiga make a clicking noise.  With one empty drive in a
quiet room it is annoying.  With two it gets on the nerves.  With three it
drives one up the wall.  And with four... well by that time you are over
the wall, and down the other side.

There is hope!	No longer will you need to stick a disk into a drive just
to get it to shut up.  I hereby unveil:

noKLICKstart

A program to patch your V1.2 Kickstart disk.  After the modification the OS
will test for disk insertion silently.	If you have an Amiga with Kickstart
in ROM, you have just discovered a disadvantage of Kickstart in ROM.  (A
RAM based version is possible...)

All that is needed is to patch Kickstart.  You need to change one solitary
bit, and then fix the checksum.  Which bit??  heh... heh... there are
2,097,152 choices... what's it worth to 'ya?  Nothing???  Ok then, I'll
tell you.  Change the long word at $00FE99E8 from $086B001 to $08EB001.  I
don't know where the real checksum is kept, so I just mangle the Copyright
notice by changing $00FC007C from $6D6F646F to $6CEF646F.

This turns a "BCHG" instruction into a "BSET".

Maybe you'd like a program.  It's called noKLICKstart and came with this
arc.  It will patch a V1.2 Kickstart to be a V1.2 noKLICKstart.  Naturally
it is compatible with all software.  The program should be 1324 bytes long.


-------------------------- possible problems ------------------------------

Q> I get this message-> "You can't fool me! :-) That's not an unmodified
V1.2 release Kickstart!!".

A> You are *not* running the proper version of Kickstart.  If you are using
the "Gamma 1" release you will get this message.
   This message will also show up if you are running a version of the
operating system that was not available at the time of this writing.

---------------------------------------------------------------------------

Q> My drives keep making noise, even after I have inserted and removed a
disk from them.

A> You drives are incompatible with noKLICKstart.  Sorry!  No damage has
been done, but you should discontinue use.



---------------------------------------------------------------------------


Technical mumbo jumbo:	It's quite simple, really.  The /CHNG signal is set
low and latched by the drive when a disk is pulled out.  In order to see if
a disk has been inserted the latch must be unlatched.  This is done by
stepping the head.  Normally the Amiga goes from track 0 to 1 and back.
This is what makes the noise.

Now these drives all have track 0 sensors.  You can't make the drive go
past track zero.  You can, however, reset the latch by _trying_ to step out
past track zero.

My assumption was that any transition of /STEP would reset the /CHNG latch.
This has held true for all drives.  I also assumed that before /STEP got to
the stepper it would pass through a gate that would block it if the
DIRection was outwards and the track zero sensor was active.  Not for some
drives.

"Matsushita" and "Mitsumi" drives are not compatible with noKLICKstart.


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{o O} .
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