Switching From PAL To NTSC And Back Again.

Barry Walker

These two very small and simple assembler programs switch ECS and AGA machines between the two standard TV modes used today, PAL and NTSC.

The two executables are each only 52 bytes in size and can be called from a CLI or from an ICON if you generate one.  They can also be placed into the ~Startup-Sequence~ to force either PAL or NTSC mode deliberately during a reboot proceedure.  This eliminates the need to stop at the ~Early Startup Screen(s)~ to select the required mode.

These code sections are free issue and were compiled using the DevPac2/3 Assembler/Monitor package from HiSoft.  Remember to disable icon saving and debug information to obtain a reliable and small executable size.  (With little or no alteration they should compile with most assemblers.)  These code sections were compiled with 'a68k' and linked with 'blink' also and all was OK.

There is no reason why the code can't be placed inline any major code you write to force a particular TV mode of your choice...

(In future issues of the magazine I will be describing and releasing ARexx and AmigaBASIC methods of doing the same thing plus numerous other hardware hacks using these two interpreters.)

Before experimenting with PAL/NTSC mode switching ensure that the TV or monitor connected to the ECS/AGA AMIGA can handle the two modes.  DO NOT try it on TVs or monitors that CANNOT handle them as damage to the display could be the result.

Enjoy... :)


                                    ;Assembler source to switch video
                                    ;to NTSC format.
                                    ;Compiled under ~DevPac3~.
      move.w   #0,$dff1dc           ;Set hardware to NTSC mode.
      move.l   #0,d0                ;Set return code as OK.
      rts                           ;Exit program.


                                    ;Assembler source to switch video
                                    ;to PAL format.
                                    ;Compiled under ~DevPac3~.
      move.w   #32,$dff1dc          ;Set hardware to PAL mode.
      move.l   #0,d0                ;Set return code as OK.
      rts                           ;Exit program.

To save the hassle of editing these files OR copying out manually into an editor the sources are separate files and can be downloaded...


The Legal Stuff:-

These programs are Freeware and no profit will be made from them, also all of the files must remain unaltered and intact including this one.  The author is not responsible for any damage to, or loss of, or failure of equipment or data caused in any way by the use of these programs.  There is NO warranty with the use of these software releases and YOU USE THEM AT YOUR OWN RISK.

Testing Evaluation:-

An A1200(HD) in 2MB, 6MB and 10MB modes using trapdoor memory AND/OR PCMCIA memory expansions.  Also tested on an A600(HD) in 2MB and 6MB modes.  All test conditions were/are running STANDARD KS2.0x to 3.1x, and using standard ~topaz 8~ fonts throughout.

I have no idea what a strange configuration setup will create so refer to the ~The Legal Stuff~ above.


1) DISCONNECT any faulty equipment under test from the MAINS supply.
2) If a DC supply is used do NOT reverse polarity the connections.
3) Do NOT power up any electronic item until it is safe to do so.
4) CHECK and RECHECK all of your construction and repair work thoroughly.
5) Handle ALL tools used with care.
6) Beware of ALL types of solvents, glues and etching fluids.
7) NEVER leave a soldering iron switched on unattended.
8) KEEP everything OUT of the reach of small children.
9) Switch OFF the AMIGA before disconnecting or connecting any hardware.
10) And finally read 1) to 9) again.


Mr Barry Walker,  G0LCU.

Email:- wisecracker@tesco.net

URL:- http://homepages.tesco.net/wisecracker/G0LCU.HTM

Author of the ~TestGear?~ projects in the ~hard/hack~ drawer of AMINET.

A very useful HardWare related site,  (C)  Anthony Hoffman, for modifications, schematics, repairs and the like is:-


RIYAN Productions