The universal Atari assembler

rg-asm

Name: rg-asm
Author: Reservoir Gods

Free universal 680x0 and DSP 56k assembler targeting Atari systems.

Download rg-asm 0.9.6

Linux-x64 · 5.0 MB · 2026-10-28

All builds: Linux x64 · Linux arm64 · macOS Apple Silicon · macOS Intel · Windows x64

Release notes (v0.9.6)

Key features

Universal Input: Compatible with all existing Atari assembler dialects, including: vasm, Devpac, RMAC, TurboAsm, GNU GAS and others.
Universal Output: Built-in linker, can assemble to a runnable PRG, or emit objects for linking with external tools.
Universal CPU: Supports the full 680x0 line — 68000 through 68060, FPUs (68881/68882), and even all the ColdFire models.
Motorola DSP 56001: Standalone assembly for Atari Falcon DSP kernels, with support for all the key output formats.
Mixed-Mode 68k & DSP: Embed DSP56001 code directly within 680x0 source files, sharing symbols, equates, and structured data offsets.
Universal Binaries: Cross compile from native binaries for Linux, Mac and Windows. Single executable with no dependencies - simply download, unzip and run.
Complete Syntax: Macros, conditionals, incbin, org/sections, equates, alignment and linkage. Supports every major Atari assembler syntax.
Diagnostics & Metrics: Shows instruction cost on every CPU. Per function breakdown of cycle and byte cost. Every metric can be output to json to be processed by other tools.
Language Server: Built-in stdio LSP daemon (rg-asm --lsp) brings Atari assembly into modern editors (VS Code, Cursor, Neovim, Helix). Instant diagnostics, autocompletion, jump-to-definition, and cycle-cost hover inspection as you type.
68k Inside: rg-asm is built around a full 68k emulator, so it can fully understand every instruction. Can even reorder instructions to benefit from pipeline pairing.

rg-asm; assemble & link

$ rg-asm hello_gemdos.s
  █▀▀▄ █▀▀▀
  █▀█▄ █ ▀█   RESERVOIR GODS
  ▀  ▀ ▀▀▀▀   rg-asm 0.9.6 · 680x0 & DSP 56k assembler
 
  ✓ Assembling hello_gemdos.s
  ✓ Linking HELLO.PRG (136 bytes)
  ✓ assembled 1 file in 80ms
 
┌────────┬───────┐
│ item   │ bytes │
├────────┼───────┤
│ text   │    26 │
│ data   │    22 │
│ bss    │     0 │
│ sym    │    56 │
│ reloc  │     4 │
├────────┼───────┤
│ binary │   136 │
└────────┴───────┘
$

$ rg-asm --cpu=56001 -o FILTER.LOD filter.s56
; =====================================================================
; filter.s56 — Falcon 56001 FIR filter kernel with parallel data moves
; =====================================================================
 
        org     p:$0040
 
FirFilter:
        move    #samples,r0             ; r0 -> input sample circular ring
        move    #coeffs,r4              ; r4 -> impulse response filter taps
        move    #taps-1,m0              ; enable modulo addressing on r0
        move    m0,m4                   ; and modulo addressing on r4
 
        clr     a           x:(r0)+,x0  y:(r4)+,y0  ; dual parallel prefetch
        rep     #taps-1                             ; zero-overhead loop
        mac     x0,y0,a     x:(r0)+,x0  y:(r4)+,y0  ; MAC + parallel move
        macr    x0,y0,a                             ; round accumulator result
 
        movep   a,x:<<$FFEB             ; output 24-bit sample to host port
        rts
 
✓ assembled 1 file (FILTER.LOD) in 42ms
$

$ rg-asm --cpu=68030 falcon_game.s -o GAME.TOS
; =====================================================================
; falcon_game.s — In-file 68030 host driver & embedded DSP kernel
; =====================================================================
 
        section text
Start:
        lea     DspKernel(pc),a0        ; 68030 host setup
        bsr     UploadToDsp             ; send bootstrap to DSP
        rts
 
DspKernel:
        .56001  packed, org=p:$40       ; switch target context to DSP56001
        movep   x:<<$FFEB,x0            ; read 24-bit param from host port
        do      #64,_poly               ; DSP coprocessor transform loop
        mpy     x0,y0,a  x:(r0)+,x0 y:(r4)+,y0
_poly:
        rts
        .68000                          ; restore host 68k context (auto even)
 
✓ assembled 68030 host + inline DSP56001 kernel into GAME.TOS
$

$ rg-asm hello_gemdos.s --listing
  █▀▀▄ █▀▀▀
  █▀█▄ █ ▀█   RESERVOIR GODS
  ▀  ▀ ▀▀▀▀   rg-asm 0.9.6 · 680x0 & DSP 56k assembler
 
  ✓ Assembling hello_gemdos.s
  ✓ Linking HELLO.PRG (136 bytes)
  ✓ assembled 1 file in 80ms
 
┌──────────┬─────────────────────┬───────┬───────┬──────┬───────────────────────────────────────┐
│ addr     │ bytes               │ 68000 │ 68030 │ pair │ asm                                   │
├──────────┴─────────────────────┴───────┴───────┴──────┴───────────────────────────────────────┤
│ start                                                                      26 B · 176/109 cyc │
├──────────┬─────────────────────┬───────┬───────┬──────┬───────────────────────────────────────┤
│ 00000000 │ 41 FA 00 00         │     8 │     5 │    · │ lea msg(pc),a0                        │
│ 00000004 │ 2F 08               │    12 │     5 │    · │ move.l a0,-(sp)                       │
│ 00000006 │ 3F 3C 00 09         │    12 │     7 │    · │ move.w #9,-(sp) ; Cconws              │
│ 0000000A │ 4E 41               │    34 │    20 │    · │ trap #1                               │
│ 0000000C │ 5C 8F               │     8 │     8 │    · │ addq.l #6,sp                          │
│ 0000000E │ 3F 3C 00 07         │    12 │     7 │    · │ move.w #7,-(sp) ; Crawcin             │
│ 00000012 │ 4E 41               │    34 │    20 │    · │ trap #1                               │
│ 00000014 │ 54 8F               │     8 │     8 │    · │ addq.l #2,sp                          │
│ 00000016 │ 42 67               │    14 │     9 │    · │ clr.w -(sp) ; Pterm0                  │
│ 00000018 │ 4E 41               │    34 │    20 │    · │ trap #1                               │
├──────────┴─────────────────────┴───────┴───────┴──────┴───────────────────────────────────────┤
│ ── DATA ───────────────────────────────────────────────────────────────────────────────────── │
├───────────────────────────────────────────────────────────────────────────────────────────────┤
│ msg                                                                                      22 B │
├──────────┬─────────────────────┬───────┬───────┬──────┬───────────────────────────────────────┤
│ 00000000 │ 48 65 6C 6C 6F 20 … │       │       │      │ dc.b "Hello from rg-asm!",13,10,'$',0 │
│          │                     │       │       │      │ even                                  │
└──────────┴─────────────────────┴───────┴───────┴──────┴───────────────────────────────────────┘
$

$ rg-asm hello_gemdos.s --functions
  █▀▀▄ █▀▀▀
  █▀█▄ █ ▀█   RESERVOIR GODS
  ▀  ▀ ▀▀▀▀   rg-asm 0.9.6 · 680x0 & DSP 56k assembler
 
  ✓ Assembling hello_gemdos.s
  ✓ Linking HELLO.PRG (136 bytes)
  ✓ assembled 1 file in 80ms
 
┌──────────┬───────┬───────┬───────┐
│ function │ bytes │ 68000 │ 68030 │
├──────────┼───────┼───────┼───────┤
│ start    │    26 │   176 │   109 │
│ msg      │    22 │     0 │     0 │
├──────────┼───────┼───────┼───────┤
│ total    │    48 │   176 │   109 │
└──────────┴───────┴───────┴───────┘
$

Quick start

rg-asm main.s util.s                           # assemble and link → MAIN.PRG
rg-asm --obj player.s                          # emit relocatable object for C linkers
rg-asm game.s --listing                        # per-instruction cycle timing & metrics
rg-asm falcon_game.s                           # 680x0 + inline Falcon DSP mixed-mode

Verify

After unzipping, check the extracted files (the archive includes SHA256SUMS):

sha256sum -c SHA256SUMS

rg-asm

Key features

Quick start

Verify

Learn more