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All versions of the Atari OS may be available for download here as well.
Version 3.4, 2005-11-26
By Freddy Offenga
400/800 10kB OS roms
Rev. TV Date CRC-32 Part Nr(s)
~~~~ ~~~~~ ~~~~~~~~~~~ ~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
A NTSC 1979 0xc1b3bb02 CO12499A, CO14599A, CO12399B
A PAL 1979 0x72b3fed4 CO15199, CO15299, CO12399B
B NTSC 1981 0x0e86d61d CO12499B, CO14599B, 12399B
B PAL (?) (?) (?)
XL/XE 16kB OS roms
Rev. System Date CRC-32 Part Nr(s)
~~~~ ~~~~~~ ~~~~~~~~~~~ ~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~
10 1200XL 10/26/1982 0xc5c11546 CO60616A, CO60617A
11 1200XL 12/23/1982 (?) CO60616B, CO60617B
1 600XL 03/11/1983 0x643bcc98 CO62024
2 XL/XE 05/10/1983 0x1f9cd270 CO61598B
3 800XE 03/01/1985 0x29f133f7 C300717
4 XEGS 05/07/1987 0x1eaf4002 C101687
(?) This information is missing. If someone can supply this info,
please write me an e-mail.
The 400/800 O.S's consist of three ROMs (two 4kB and one 2kB).
The 1200XL contains two ROMs for the OS (8k each), XL/XE's use a single
16k ROM and the 16k XEGS OS is stored in a 32k ROM (together with 8k
BASIC and 8k for Missile Command).
Origins of ROM information
400/800 rev.A NTSC All information from OS board C012989 (Rev D) and
400/800 rev.A PAL All info found in two Atari 400's and Atari 800
ROM module CX801.P
400/800 rev.B NTSC Information from a ROM dump and the rev.B source
listing. The part numbers were listed in the
catalog from 'Best Electronics'. According to
"Mapping the Atari" rev.B ROMs have a "B" at the
end of the part number, therefore I figure these
part numbers are from rev.B.
400/800 rev.B PAL Could exist, since the NTSC version exists and
there’s some conditional PAL/NTSC assembly in
the rev.B source code
1200XL rev.10 PAL/NTSC All info found in an Atari 1200XL. The XL/XE
rev.2 source code refers to it as rev.10.
"Best Electronics" calls it rev.A.
1200XL rev.11 PAL/NTSC Refered to rev.11 by the XL/XE source code.
"Best Electronics" calls it rev.B.
XL/XE rev.1 All info found in an Atari 600XL
XL/XE rev.2 All info found in an Atari 800XL
XL/XE rev.3 All info found in an 800XE
XL/XE rev.4 All info found in an Atari XE Game System
O.S. Authors and dates
The following info is from the Atari XL/XE rev.2 source code.
Revision A (400/800)
D.Crane / A.Miller / L.Kaplan / R.Whitehead
Revision B (400/800)
Fix several problems.
M.Mahar / R.S.Scheiman
Revision 10 (1200XL)
Support 1200XL, add new features.
H.Stewart / L.Winner / R.S.Scheiman /
Y.M.Chen / M.W.Colburn 10/26/82
Revision 11 (1200XL)
Fix several problems.
Revision 1 (600XL/800XL)
Support PBI and on-board BASIC.
R.S.Scheiman / R.K.Nordin / Y.M.Chen 03/11/83
Revision 2 (600XL/800XL)
Fix several problems.
Bring closer to coding standard (object unchanged)
The following OS roms originate from rare Atari 8-bit systems.
Since I don't own any of these (unfortunately), I don't have much
information about these roms. Who can help me?
I've got two 16K rom dumps from the 1450XLD. Both ID's are rev.3.
The first dated 3/23/1984 comes from the 'Pooldisk Too' CD-ROM
(filename: 1540os3.v0) and the second dated 6/21/1984 was send to
me by Nir Dary (filename: os1450.128). Main differences between
these two are in the first 3K ($C000 - $CBFF).
The XL/XE OS rev.3B is from an Atari from Arabia. It's probably based
on rev.3. There are changes in the fonts (Arab characters) and several
patches in the code. More info at:
Rev. Found in Size CRC-32 Date
~~~~ ~~~~~~~~ ~~~~~ ~~~~~~~~~~~ ~~~~~~~~~~
3 1450XLD 16kB 0x0d477aa1 3/23/1984
3 1450XLD 16kB 0xd425a9cf 6/21/1984
3B 65XE 16kB 0xf0a236d3 7/21/1984
- The modified september Atari 400/800 computer operating system
listing, revision B, (c)1982 Atari.
- The Atari O.S. source code rev.2, (c)1984 Atari.
- Atari XL addendum Atari home computer system operating system
manual: supplement to Atari 400/800 technical reference notes.
- Best Electronics, catalog of Atari 8-bit parts.
- Mapping the Atari, revised edition, Ian Chadwick, Compute! books
- Nir Dary for the rev.2 source code, rom dumps and the 1200XL.
- Sijmen Schouten for his reconstructed 400/800 Rev.B source code.
- Stephen Sheppard for 400/800 Rev.A/NTSC information and rom dumps.
More info on what is maybe either the 1985 or 1987 XL/XE OS versions listed
above. From ST*ZMAGAZINE #36, Sept. 1, 1989 (as reprinted in PSAN Nov 89):
by Mark Elliot, Innovative Concepts
The following changes have been incorporated in the 130XE computer.
The O.S. has minor changes like:
A) The MEMORY TEST (from SELF TESTS) tests the extra 64K now! (in 4 squares)
B) Also, the MEMORY TEST checks the first 48K over TWICE as fast as before!
C) The KEYBOARD TEST has the F1-F4 keys missing on top. (function keys),
although the code that interprets them is probably there (like XEGS).
D) Also, it types out "COPYRIGHT 1985 ATARI" at the keyboard test, when all
tests are done. (compared to COPYRIGHT 1983 ATARI, before)
E) And, the O.S. chip itself, is on a 27256 EPROM, but only half of it is
used! (comprared to the original, which was on a 16K x 8 ROM, 27128 comp.
In the 400/800, memory location 58383 ($E40F) contains 56 if running Rev. A,
or contains 0 if running Rev. B of the Atari Operating System. At the Atari
BASIC READY prompt, enter "? PEEK(58383)" to read this location.