Subject: UPGRADE: The Dual OS Switch

The Atari OS Switch
(based on an article in ANTIC)

Remember, do this at your own risk!

PARTS: DPDT mini switch (1)
       28 pin socket (1)
       Thin wire (about a foot or so)
       Second OS ROM chip.

Step 1:	Remove the OS ROM from your XL/XE computer

Step 2: Solder a 28 pin socket on top of the OS ROM, pin to pin.

Step 3: This is a diagram of the DPDT switch.
        All letter references [A] refer to the positions
        marked below.

Switch: +---+
        |A B|
        |C D|
        |E F|

Step 4: Connect [A] to [F]

Step 5: Connect [B] to [E]

Step 6: Bend up pin 20 on both of the ROMs.

Step 7: Connect pin 28 on the ROM/socket to [E]

Step 8: Connect pin 22 on the ROM/socket to [F]

Step 9: Connect pin 20 of the original ROM to [C]

Step 10:Connect pin 20 of the new ROM to [D]

Step 11:Plug the new ROM into the socket.

Step 12:Plug the package of ROMs into the motherboard.

You can now switch between OSes.  I used inline pins to go
to pin 20 on both ROMs; lets me make changes.

You'll have to reboot if you try switching with power on.

Hope this helps,

Dave Paterson

Craig Lisowski (