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 1.09
- Numerous security fixes, no more stack overflow issues when compiling hostile code.
- Numerous bug fixes.
In addition to included Windows binary, ATasm compiles
cleanly under Linux, MacOS/X or any platform with the GNU C compiler.
Download the current and older releases from
(includes Windows binary,
complete source code, documentation and sample Mac/65 source files)
The latest 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 via the SourceForge project.