Open Source Mac Assemblers

ACME is a free cross assembler released under the GNU GPL. It can produce code for the following processors: 6502, 6510 (including illegal opcodes), 65c02 and 65816. ACME supports the standard assembler stuff like global/local/anonymous labels, offset assembly, conditional assembly and looping assembly. It can include other source files as well as binaries while assembling. Calculations can be done in integer or float mode. Oh, and it is fast.

Z88DK is a complete Z80 / Z180 development kit that includes C compiler, assembler, linker, a tool for generating executables in a number of formats, and miscellaneous other tools. Over 80 machines are directly supported out of the box including standalone Z80 and Z180 embedded systems. Z88DK's extensive assembly language libraries give it significant performance advantages over other Z80 C Compilers. Building software for standalone or generic Z80 systems: https://www.z88dk.org/wiki/doku.php?id=libnew:target_embedded Visit us at github for the current version with bugfixes and new features: https://github.com/z88dk/z88dk

A cross assembler for the ubiquitous Intel(tm) 8048 family of microcontrollers. Also supports compatible parts such as the 8035, 8039, 8049, etc. Binaries are available for Windows, Linux and Mac OSX.

Dev65 is a macro assembler, linker and librarian suite for the 6501, 6502, 65C02, 65816 and 65832 family of microprocessors coded in Java for portability. The code is based on a framework that could support other system architectures.

asxa: Cross Assembler for NXP XA-51 Microcontrollers. Included is a monitor in XA assembly language with a disassembler a a debugger.