xais Andre Fachat's open-source 6502 cross assembler. I, Cameron Kaiser (firstname.lastname@example.org), am the current maintainer, and bug reports and questions should now go to me.
xa is Copyright © 1989-2022, André Fachat,
Jolse Maginnis, David Weinehall and Cameron Kaiser. All rights reserved.
Additional contributors: Fabien Nuñez, Mikkel Holm Olsen,
Adam Sampson, Alessandro Gatti, Simon Rowe, Dan Horák, Frederic Cambus,
Sam Falvo, Stephen Kitt, Bas Wassink.
xa is distributed under the
GNU Public License v2. The current maintainer is
For other Floodgap-maintained packages, see the Floodgap Software listing.
xais a high-speed, two-pass portable cross-assembler. It understands mnemonics and generates code for NMOS 6502s (such as 6502A, 6504, 6507, 6510, 7501, 8500, 8501, 8502 ...), CMOS 6502s (65C02 and Rockwell R65C02) and the 65816.
Key amongst its features:
o65relocatable objects with a full linker and relocation suite, as well as "bare" plain binary object files
xa's eventual companion disassembler is
dxa, a moderately hacked-up version of Marko Mäkelä's
d65disassembler. This is still alpha and is available as a separate distribution until it is stabilized enough to be part of the
xa2.3.13 is released. This is a bugfix release of the long-lived 2.3.0 series branch, and is probably, honestly, really, no kidding, why won't you believe me, I am not a crook, the final 2.3.x release before 2.4.
xa-2.1.4f-amiga.lhawith the 2.1.4f Amiga binaries, as well as the "smakefiles" and "SCOPTIONS" files to compile under SAS/C. This was provided by Pasi Ojala. Please note that this version is not supported. If you want to browse other prior versions, look in
dists/unsupported/. Please do not send bug reports in about these versions.
xa should compile out of the box on just about any Unix or
Unixy thing, and will probably compile on other systems that support ANSI
C as well. Please see the
README.1st file for more detailed
instructions. It is tested and validated on AIX (gcc),
Linux/ppc64le (gcc and clang), Mac OS X
(gcc on PowerPC, and clang
on Intel x86_64 and Apple silicon) and NetBSD/macppc and
manformat since 2.3.0. You can read them here, converted with
"I developed the first version of xa on my old Atari ST to build programms for my selfbuilt computer CS/A65. After my Atari broke I ported it to Linux (ported? It compiled right out of the box!) and when I had to develop a programm for a friend of mine, I compiled it on an Amiga without errors. Until the beginning of 1992 I made more improvements, until it came to version 2.0.7. Since then I only very occasionally worked on it, up to version 2.0.7d. When I decided to push my selfbuilt OS to a new level in 1996, I needed more important improvements, like o65 object format and a linker and all that."
xais now officially accompanied by
dxa, its companion disassembler.
dxais a rudely hacked version of Marko Mäkelä's
d65package, with some extra features and altered output to allow "perfect" disassembly (which is to say, you can take an arbitrary object, run it through
dxa, take what it spits out, run it back through
xa, and get the binary you started with). It also has features for intelligently labeling code and data sections and multiple output formats, and can understand undocumented and CMOS opcodes (65816 not yet).
dxa is new and not well tested, I have not included it
as part of the standard
xa distribution and it is offered here
separately. Please consider it to be alpha software only and expect bugs.
Refer to the readme for instructions on installation.
d65, is distributed under GPL v2.
There are also many fixes in this version, including properly getting the very
last byte for files that load all the way to $ffff and correctly
(IMNSHO) truncating files that load beyond (thanks Malte), fixes for bugs with
clang-built dxa generating incorrect code, fixes for an
issue with the C preprocessor, and more flexible BASIC header detection.
Note that clang-built dxa does behave differently than
gcc-built dxa and more research is needed (currently the
only guarantee is that both will generate an assembly file which will
assemble to identical binaries).
dxa is based on
manformat; here is the