Atari 400/800/XL/XE/XEGS systems

XL/XE systems

· EASTER EGG: When running the full diagnostic test on a 1200XL, the keyboard will spell out the programmer’s name, “michael colburn”.  This was removed with the 600XL and 800XL, with the keyboard test now spelling out “Copyright 1982 Atari”.

· Another neat effect with the 1200XL’s diagnostic program is that the system’s L1 and L2 LEDs alternate with each block of memory tested.

· The 1200XL boots up to a screen with “ATARI” in large letters shown with the famous scrolling rainbow color effect (picture #1).  2 different versions of this boot-up screen are believed to exist - one with the Atari logo, and one showing the programmer’s name.

· The last run of 65XEs that were made in China used modified 130XE motherboards.  To upgrade it back to 130k, add 2 RAM chips (at U11 and U12) and add a CO25953 chip to U3 (remove the 3 resistors first).

· Multiple versions of the OS code were made - see for details. The keyboard test in the 600XL/800XL OS will type out a “1983” date; the XEs will type out “1985”. The memory test in the XEs runs faster, and can test for extended 64K of memory (shown as 4 large blocks at the bottom of the screen). Although the XEGS only has 64K of memory, the test program is essentially the same as the 130XE and is capable of testing extended memory.

· Several programs originally designed for the 400/800 systems will not run on any XL systems, or newer XE/XEGS systems (having an OS with a new version number, self-test/memory-test/keyboard-test, larger RAM chips, etc.), because of changes made to the original 800 OS.  To get an overview or see a chart of these changes, refer to Antic magazine Volume 3, Number 2 (June 1984), pages 10-14; (  To correct this problem, Atari issued a set of Translator disks, which loaded the original 800 OS versions (pictures #2 and #3) into your XL/XE prior to running a disk-based program. To use the Translator disks with cassettes, press START + SELECT when it’s finished loading. Here’s a list of reported titles that are incompatible (the list is maintained at:

Apple Panic
Astro Chase
  (the original works on everything. Parker Bros version only works on 400/800/1200XL. Exidy version only works on XL/XE)
Atari Word Processor
Atlantis (some versions!)
Attack at EP-CYG-4
(patch for XL/XE available:
Dancing Feats
Demon Attack
Dreadnaught Factor, The
File Manager 800+
Forbidden Forest
(later versions by different companies work ok on XL/XE!)
Fort Apocalypse (cart version is 400/800 only! tape+disk versions work ok on XL/XE!)
Galahad And The Holy Grail
Jawbreaker II
Jet Boot Jack
(can be found on various tapes/disks; at least the re-release version by Byte Back works alright on XL/XE computers!)
K-Razy Antiks
K-razy Kritters
Leo's 'Lectric Paintbrush
Leo's Links
Letter Perfect
(before v6)
(vr. 1.00, orange)
Mario Bros. ('83)
Micro Illustrator
Monkey Wrench
Monster Maze
Ms. Pac-Man
(has problems with newer XE/XEGS computers!)
M.U.L.E.(early release only)
Nautilus (holding down START skips title screen, which is where it locks up)
Pac-Man Jr.
Picnic Paranoia
Pool 1.5
Pool 400
Protector II
QS Forth
Rack 'Em Up
(holding down START or SELECT skips title screen, which is where it locks up)
Space Dungeon
Squish 'Em
Super Pac-Man
Text Wizard
(early release only!)

· BUG: The diagnostic program for the 600XL and 800XL still show the 1200XL keyboard layout.

· BUG: The operating system has an inherent flaw in the S: handler routine. For example, using certain (S: handler) values meant for use by the E: handler, such as 155 (EOL/line feed) and 125 (clear-screen) end up being interpreted by the S: handler instead. The following BASIC program illustrates this problem:

1 GR.15+16
2 COLOR 125: PLOT 0,125:DRAWTO 50,125
3 COLOR 155: PLOT 0,155:DRAWTO 50,155
4 GOTO 4

If the COLOR values are changed to 1 and 2 respectively, you’ll see that the programs original intention was to draw 2 differently-colored horizontal lines.

· BUG: The infamous “scanline 240” bug is a result of Atari’s Antic chip not correctly disabling the display generation on what’s normally the last line of the display when in a high resolution mode (2, 3, or F).  Instead of it sending a constant HBLANK command to GTIA, it constantly sends a command to generate 2 pixels of high resolution ‘on’ pixels when the display is normally active, and then sends the HBLANK again to each scanline, but at the wrong time.  The result is the HSync pulse jumps out of step and the display becomes warped.


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