A mostly Mac/65 compatible cross-assembler
ATasm is a 6502 command-line cross-assembler that is compatible with the
original Mac/65 macroassembler released by OSS software. Code
development can now be performed using "modern" editors and compiles
with lightning speed.
ATasm is hosted at
- ATasm produces Atari native binary load object files or can
optionally target the machine state files produced by the
Plus emulator, the
emulator (version 0.9.8g or greater) and the
- Support for saving binary to .XFD or .ATR disk images
- Conditional code generation, and code block repetition
- Bank support for creating large (>64k) cartridge images or
- Rich macro support, compatible with existing Mac/65 code libraries
- Support for .ATR disk images, as well as double density and
enhanced density Atari DOS 2.x images
- Support for Atari++ state files, as well as updating other state
files to more modern formats
- Support for the .SET 6 MAC/65 directive, allowing for
compiling to offset locations
- New .BANK directive for creating large cartridge images, or for
code that uses the INITAD load vector (see the documentation for
- Atari specific assembler directives (.SBYTE,.FLOAT,etc.)
- Support for Atari "Sally" 6502 undocumented instructions
New in 1.07
- Introduction of the .BANKNUM operator, which reports the bank number of a given label. In addition, the .BANK directtive has been extended to allow manual assignment of .BANK actual bank number and reported bank number.
- Finally allow periods and leading underscores in label names.
- .SET 6 directives can now use forward defined labels in their expressions.
- Numerous bug fixes.
In addition to included Windos binary, ATasm compiles
cleanly under Linux, MacOS/X or any platform with the GNU C compiler.
Download the older 1.06 package from
(includes Win9x/ME/XP/NT/2K/XP/Vista/Win7 binary,
complete source code, documentation and sample Mac/65 source files)
In the meantime, the 1.07d preview package can be obtained
You can also view the .PDF manual
here and the
If you intend to compile the package yourself, and you do not have the zlib
compression library installed on your machine, download it from the zlib
Questions or comments? Feel free to
contact me, or visit the