A2286 Fake Disk I/O Speedup Mod

A2286 Fake Disk I/O Speedup Mod

Post by Jerry C. Hudgi » Fri, 25 Oct 1991 05:04:28



I've mentioned the A2286 Bridgeboard modification to speed up fake disk I/O
a couple of times here on the net, and I always get inquiries about it from
folks unfamiliar with it.  I've typed it in one more time and actually kept
a copy for future mail requests, but I'll go ahead and re-post it now.

The source for these modification instructions is Scott Drysdale, formerly
responsible for the Janus software at Commodore.  I've performed the mod on
my own A2286, and it works well.  This does NOT fix the A20 line problem on
the A2286, so it won't help you with Windows 3.0.

BTW, with or without the hardware mod, you can speed up your fake disk I/O
with the Addbuffers command.  This is especially useful if you're using the
MakeAB-type autoboot C: drive and you've set up a separate disk partition
for the container file referenced by SYS:PC/System/ABOOT.CTRL.  Addbuffers
will speed up any hard drive partition, but the Bridgeboard is really helped
out by this.  If you have the memory, add a large chunk; I use 200.  These
lines appear at the beginning of my S:Startup-Sequence:

    SetPatch >NIL: R         ; patch system functions
    Sys:System/FastMemFirst     ; use chip memory last
    Stack 8192
    Addbuffers df0: 30          ; cache buffers for floppies
    Addbuffers df1: 30
    Addbuffers dh0: 200         ; cache buffers for AmigaDOS boot partition
    Addbuffers dh1: 200         ; cache buffers for MS-DOS boot partition
    cd c:
    echo "Amiga Workbench Disk. Release 1.3.3 version 34.34"
    BindDrivers                 ; wake up the Bridgeboard
    .
    .
    .

Anyway, back to the A2286 fix, reproduced from Scott's Usenet post to:
comp.sys.amiga.emulations on 29-Jul-91:

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

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 if you know how to deal with soldering to IC pins without
toasting the IC.  [Soldering to a pin isn't required if you use a patch
wire with a push-on socket end.  -JH]

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.

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

64 Monte Cimas Avenue                   Usenet  : uunet!nbn!marin!jerry
Mill Valley, CA  94941-1742 (USA)       Voice   : (415) 381-2270

 
 
 

1. !!!MODS!!!MODS!!!!MODS!!!MODS!!!

              #############################
              #                           #
              #  M O D U L E   M A N I A  #
              #                           #
              #############################

             HardCore/Dance/Rave/Techno/Rock
           -----------------------------------

   Only one site on the Internet has dedicated DJs for
       mixing Computer modules....  Who is it???...

                  Digital Arts Software          
            Club Zone Collection Downloadable
           -----------------------------------
         http://www.netlink.co.uk/users/digiarts

         Manchester's Finest PD Music Collection      
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

            Most Downloaded Modules Include:  

         Chuckies-Gone (NOW ON THE AMINET ALSO)
            SPACEMAN (FROM THE LEVIS ADVERT)
        Sweet-Harmony (EXCELLENT 95 VERSION MIX)

 Tune in to us.. Turn up the bass.... Insert a Disk....

                B L A S T - O F F ! ! !

            ==============================

  Our site is being EXPANDED with much more ON-LINE

  -<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-

2. INFO moderated game design list

3. fake hard disk driver code needed!!!!!!!

4. block wrong From: address

5. Mod player and MODS?

6. Can not preview image files

7. A2286 AT / Disk drive

8. Help ! Problem with print buffering

9. X-Files theme .MOD or any X-files related .MODs

10. Mod player and MODS?

11. fs: Music mods - 50 disks for $20!

12. FS: Music Mod disk collection

13. Old Mod files & St disks