
                ATARI 'ST'  DUAL OPERATING SYSTEM
                ---------------------------------

     Here's the files to program 512K Eproms for a "Dual" OS operating
system in your ST computer.  They contain TOS 1.0  'OS' in lower half of
chips and the TOS 1.4 release ( re-worked version by Billy Bob to
support RTS/CTS flo-control ) in the upper half of the same Eproms.
     They are marked as to the correct socket to install on the
board.  TOS 1.4 version is dated 4/6/89 and TOS 1.0 is 11/20/85.

     Also included is a 'parts list' and 'step-by-step' procedure that
I used to install in my CPU.


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

   PARTS LIST:

      A - 6 512K Eproms  ( 200ns or faster ) I used 27C512's 200ns
      B - 6 1K Resistors - 1/4 watt ( Radio Shack #271-1321 )
      C - 1 SPST Toggle Switch      ( Radio Shack #275-634  )
      D - 30ga. 'Wire-Wrap' WIRE    ( Radio Shack #278-502  )
      E - About 1' ft. of 'Heat-Shrink' tubing  ( OPTIONAL )

   PROCEED AS FOLLOWS:

   First, BURN programs into all 6 proper 512K Eproms (U2,U3, etc.,).
Now, bend up Pin #1 (straight out) on ALL the Eproms (Pin #1's DO NOT
go back into the sockets).  Next, Solder a 1K resistor on EACH Eprom
between Pin #1 and Pin #28 on 'END-SIDE' of the Eproms so that that the
resistor will be BELOW the TOP level of Eprom body.  IT CANNOT BE ABOVE
BECAUSE OF CLEARANCE FOR THE POWER-SUPPLY BOARD ON STFM MODEL CPU.

   Now insert programmed Eproms into proper socket locations on CPU.

   Next, connect a wire to ALL Pin #1's of the Eproms that you bent
out previously, then run a wire from Pin #1 on U2 Eprom to one side of
the SPST Switch.

   Now, run a wire from Pin #14 of U2 to the other terminal side of
the SPST Switch.   (NOTE: I ran BOTH wires from the Switch to U2 Eprom
together in a piece of 'heat-shrink' tubing.....and twisted them....
     BUT,  BE SURE THEY ARE NOT SHORTED (or connected) TOGETHER!!!

   CHECK YOUR WORK OVER CAREFULLY FOR SHORTS BEFORE 'POWERING UP'!

   This completes the 'modification', except for mounting the toggle
switch.  At this point, you can 'Boot' the system and check it out. 
If all is well, you will get the 'desktop' and you can see which
version is currently in memory.

   I mounted my Switch just above the 'Monitor' plug connector on the
back and a little to the right, by drilling a 1/4" hole above RF
Shielding through the CPU case.


                *********************************
                      NOTICE:  NOTICE:  NOTICE:
                *********************************
    I installed this upgrade on my CPU and have had NO problems....
It runs just fine and I can select between the 2 TOS versions BEFORE
booting...with the switch set for the desired version to use.  Most
programs run with Rainbow TOS 1.4 but, due to incompatibilities of
some software, you will want the TOS 1.0 in memory instead.

     RESPECTFULLY, I ASSUME NO FURTHER RESPONSIBILITIES TO ANYONE
INCURRING ANY/ALL DAMAGES RESULTING, IF ANY FROM THEIR INSTALLING THIS
MODIFICATION!!!

              ---------------------------------------
     MANY THANKS AND APPRECIATION TO 'NIGHT OWL, DR.J, & DIONYSIS'
     FOR THEIR HELP & INFORMATION REGARDING THIS MODIFICATION.

     ALSO TO BILLY BOB FOR HIS 'MODIFICATION' TO THE TOS 1.4 "OS" TO
     SUPPORT RTS/CTS 'FLO-CONTROL' OF THE RS-232 PORT MODEM TRANSFER.


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