MODIFICATION TO TURBO PASCAL 3.01A TO RUN ON THE PORTFOLIO

Copyright (c) 1991, BJ Gleason

This document will tell you have to make a minor modification to
Borland's Turbo Pascal, version 3.01a, (TP3) to have it run on
the Atari Portfolio Computer.

WHY TP3 WILL NOT RUN

It will... it just takes an amazingly long time.  When TP3 starts
up, it tries to determine the clock speed of the computer.  It
does this by waiting for a couple of timer ticks.  On a standard
PC, these ticks are generated 18.2 times a second.  On the
Portfolio, these ticks occur about every 2 MINUTES!  So TP3 sits
and waits.

It needs to determine the speed for the DELAY and SOUND
functions.

WHAT NEEDS TO BE DONE

The result of the speed determination is stored in memory. 
Instead of calculating this variable automatically, we will place
a constant value in there, and skip the calculation.

The constant value will be hexadecimal EC.  The is the number TP3
calculates for a standard 4.77 Mhz PC.  This is the duration for
1ms.  Since the Portfolio run slightly faster, you may want to
adjust this value upwards.  I did not, since EC should be close
enough.

MODIFYING TP3

You will need TURBO.COM and DEBUG.COM.

1.   Make a copy of TP3 to patch.  DO NOT MODIFY YOUR ORIGINAL!

          COPY TURBO.COM PURBO.COM

2.   Execute DEBUG to patch PURBO.COM

          DEBUG PURBO.COM

3.   Find the speed variable.  The code for initialization it
     should be at address 199 hex.

     -U 199
     xxxx:0199      MOV WORD PTR [0012],006E
     :
     :
     -

     If you do not see this statement at address 199, look about
     for it.  If the address is different, the rest of the
     addresses will also be different.

4.   Modify the 006E to 00EC.

     -E 19d
     xxxx:019D 6E.EC<return>
     -

5.   Insert a RET instruction to skip the rest of the routines.

     -E 19F
     xxxx:019F 2E.C3<return>
     -

6.   Save it and exit DEBUG.

     -w
     Writing xxxx bytes
     -q
     C:\>

7.   To use PURBO.COM, you should set the following system
     variables  (/|\ S):

          DISPLAY EXTERNAL    -> TRACKED
          REFRESH             -> BOTH

8.   Now you should be able to edit, run and compile TP3 programs
     on the Portfolio.  The compiled programs will also run on
     the PC, but any the timing might be off, depending on the
     clock speed of the PC.

Enjoy.

bj gleason   73337,2011