From: bjbernstein@miavx1.acs.muohio.edu
Newsgroups: comp.sys.amiga.emulations
Subject: A2286 fix & questions
Date: 4 Oct 92 20:35:52 GMT
Organization: Miami University Academic Computer Service"


  For starters, here are the docs for fixing the A2286's fake disk I/O.. 
PLEASE NOTE.. 

   I attempted this fix a few months back, and fried my BB to the point 
that nobody could figure out what was wrong with it (ICs were giving proper 
signals, etc.. but NOTHING happened). All I can say is BE CAREFUL; I 
followed the instructions exactly, and it cost me a new BB.

  BTW: Newest A2286 Rom revisions are: v4.2  380682-04
                                             380683-04

    ..at least that's the ROMs my 2 month old BB has (which included Janus 
2.1)

  Also, if someone has the scematics to the A2286, what is the function of 
the pins used in this mod? Someone said the J17A pin is a +12v line (eh?)


----------------------------------------------------------------------
Group: comp.sys.amiga.emulations, Item 2193   (Current Item Range #2063 - 
#2213)
Subject: A2286 Fake Disk I/O Speedup Mod
From: jerry@marin.nbn.com (Jerry C. Hudgins), Private Use
Date: 23 Oct 91 20:04:28 GMT
 
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 partiti
    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.
  
----------------------------------------------------------------------------

  Good luck, and only do it if you can afford to fry it...

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@@ Brian Bernstein (Drone)           @@ "I'm a white dread, I'm a white   @@ 
@@ bjbernstein@miavx1.acs.muohio.edu @@  dread, so? I got a little ring   @@
@@-----------------------------------@@  and I hang it from my nose.."    @@
@@ the Fabulous Furry Freak Brothers!@@                -Jane's Addiction  @@
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@