A2286 JUMPER MODIFICATION

Problems:

1) Keystrokes are lost when A2286<->Amiga communication is taking place
   (fake disk i/o, JLINK, AREAD, AWRITE, ...).
2) Fake disk i/o, JLINK drives, AREAD, AWRITE are very slow.


Cause:

Decoding of pc i/o addresses around 06xH is incomplete, resulting in the
8042 getting accessed whenever the PC sends an interrupt to the Amiga.
This causes any keys being processed by the 8042 to get lost/corrupted,
and causes a spurious key-pressed interrupt (IRQ 9) which eats up a
lot of CPU time.


Fix:

Only attempt this is if you know how to deal with soldering to IC pins
without toasting the IC.

This is a view of the important parts of the A2286 top board.  hold the
A2286 with the three bus connectors toward you and component side up.


      ....................
     |                    |
     >     8742 (U72)     |
     |                    |
      .....*..............


      ..............
     |              |
     > BIOS 1 (U57) |
     |              |
      ..............

      ..............
     |              |
     > BIOS 0 (U56) |
     |              |
      ..............
                            J17A
   .*.............................
   ...............................
                            J17B


1) Lift the starred pin (6) of U72 out of the socket.  Be careful, as this
   isn't your garden variety AT clone 8042 and you'll have to order one
   from Commodore through a dealer or something.

2) Attach a wire to it (preferably through a single machine pin socket
   to avoid soldering to the 8742 itself).

3) Attach the other end of the wire to the starred pin (2nd from left) of
   J17A.  This is technically pin 30 of J17A, since pin 1 is on the far right,
   but hey - it's easier to count to 2.

4) Kiss your warranty goodbye.


