Atari 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” (see video).  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.

• 2 different versions of the 1200XL OS exist – Rev A (or “10”) and Rev B (or “11”).  Both boot up to a screen with “ATARI” in large letters shown with the famous scrolling rainbow color effect, but Rev A doesn’t have “®” after Atari (picture #1) and Rev B does (picture #2).  Rev B fixed several bugs and improved compatibility with the 400/800 software, and was the baseline for the 600/800XL OS.

• Many people, noting that the 800XL is advertised as a 64K machine, assume that it gives you 16K more RAM (random-access memory) for programming than the 48K Atari 800.  However, the 800XL actually has about 20 fewer bytes of free RAM in BASIC than the 800 does.  Apparently, Atari intended to "bank select" (swap ROM for RAM) the extra RAM in certain programming environments.  As a result, they added some "pointers" in lower RAM to help the Operating System (OS) keep track of which RAM/ROM configuration was in effect.  These pointers are largely responsible for using up the extra bytes of RAM noted above.

• 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.  To check which version you have, in Atari BASIC type “PRINT PEEK (65528).

See this site 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 XL/XE systems because of changes made to the original 800 OS.  To get an overview or see a chart of these changes, refer to Antic 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 #3 and #4) 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.  Some of these have been patched by homebrew programmers over the years to work with the XL/XE.  Here’s a list of reported titles that are incompatible (the list is maintained here):

Apple Panic
Aquatron
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 (only early releases?  Most copies work on XL/XE)
Attack at EP-CYG-4
Bacterion! (hangs up after a few screens)
Bandits
Chicken
Crossfire (keyboard doesn’t work on XL/XE)
Dancing Feats
Demon Attack (Activision disk re-release fixed for XL/XE)
Disk 50
Dreadnaught Factor, The
Drelbs
FileManager+ (AKA FileManager 800+)
Forbidden Forest (only early releases?  Later versions by different companies work on XL/XE)
Fort Apocalypse (cart version is 400/800 only!  Tape+disk versions work on XL/XE)
Forth
Galahad And The Holy Grail
Ghost Hunter
Go (Stack Computer Services)
Gorf
Jawbreaker II
Jet Boot Jack (only early releases By Synapse?  All tapes/disks and Byte Back versions work on XL/XE computers)
Jr. Pac-Man (prototype)
Juggler
K-razy Antiks
K-razy Kritters
K-star Patrol
Kangaroo (prototype)
KoalaPainter
Leo's 'Lectric Paintbrush
Leo's Links
Letter Perfect (before v6)
LogicMaster
Mac/65 (v1.00, orange)
Mario Bros. ('83)
Maze
Micro Illustrator
MicroMaestro
Monkey Wrench
Monster Maze
Ms. Pac-Man (has problems with later XE/XEGS)
M.U.L.E. (early release only?)
Nautilus (holding down START skips title screen, which is where it locks up)
Picnic Paranoia
Pinball Construction Set (original release)
Pool 1.5
Pool 400
Protector II
QS
Rack 'Em Up
Rampage (only works on the XEGS if keyboard is plugged in)
Shamus (holding down START or SELECT skips title screen, which is where it locks up)
Slime
Snapper
Space Dungeon (5200 conversion)
Space Invaders (wrong sound f/x for appearance of Mystery ship, and none for shooting it)
Squish 'Em
Story Machine (only cartridge.  Disk versions work on XL/XE)
Super Pac-Man (prototype)
Synassembler
Text Wizard
VT-10-Squared
Zaxxon (early 32K release only!  Most copies of 32K disk work on XL/XE, as do earlier 16K cassette and 16K cartridge)

• 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 diagnostic program for the 600XL and 800XL still show the 1200XL keyboard layout.

• 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.

• BUG: Many 3^rd-party cartridges won’t fit in the 1200XL’s cartridge port.