Arnold for Amiga is a port of Kevin Thacker's Arnold, the Amstrad CPC
emulator, to 68k AmigaOS 3.x with AGA. It emulates the CPC 464, 664 and
6128 as well as the CPC 6128 Plus and the GX4000 console: Plus cartridges,
disks and snapshots, with sound through Paula, on PAL and NTSC displays.
Released with Kevin's blessing, under the GPL.
Requirements
------------
- AmigaOS 3.1 or later, AGA.
- A 68040 or better: PiStorm32 (Emu68), 68060 cards, or BigMig on MiSTer.
No FPU needed.
- lowlevel.library is optional (CD32 pads).
- Fast vertical scrolling uses about 0.5 MB more chip RAM; with less
free, Arnold falls back to the plain display (NOVSHIFT forces that).
What to expect
--------------
Arnold for Amiga targets PiStorm/Emu68-class machines. On an A1200 with
a PiStorm32 CM4, the games tested run at full speed (Sonic GX at 49 fps
without frame skip, measured: 78% of the frame time, with a slight
slowdown only in very fast vertical scrolls). On BigMig (MiSTer) games
currently run below full speed; use Arnold-060 with frame skip. Real
68060 accelerator cards have not been tested; expect games below full
speed. 68030 machines are too slow for games.
Installation
------------
Copy the Arnold drawer anywhere. Start one of the presets:
Arnold PiStorm 68040 build, sound on, frame skip up to 3
Arnold BigMig 68060 build, sound on, frame skip up to 3
or the program itself. HELP opens the menu (media, settings, controls).
README.txt in the drawer has the details, keys and Shell options.
The drawer includes the Plus system cartridge (BASIC 1.1, AMSDOS and
Burnin' Rubber) and the CPC 464/664/6128 system ROMs, so CPC disks and
the built-in game work at once. Supply
your own cartridge (.cpr) and disk (.dsk) images.
Features
--------
- CPC 464, 664, 6128, 6128 Plus and GX4000 models, picked in the menu.
- Plus / GX4000 cartridges (.cpr), standard and extended disks (.dsk) in
drives A and B, snapshots (.sna).
- PAL or NTSC (or as Workbench); on NTSC the CPC still runs at its own
50 Hz, so games and music keep their correct speed.
- Paula sound (8-bit stereo); frame skip keeps heavy games at full speed.
- Menu with pull-down options, per-game settings, keyboard map, IFF and
PNG screenshots; Workbench presets with ToolTypes.
- Joystick in port 2 (normal or CD32 pad, chosen in the menu) and the
keyboard as a joystick.
- Fixes to the Arnold core found during the port: Plus soft scroll,
raster and DMA interrupt timing, the Z80 overflow flag, disk image
loading and more (offered upstream as patches).
Known issues
------------
- Sonic GX plays at full speed on a PiStorm, with only a slight
slowdown in fast vertical scrolls.
- NTSC shows fewer lines than PAL, so games drawn to the screen edges
lose their top and bottom; use PAL for the full picture.
- Pinball Dreams tears and can crash when the ball is launched (still
under investigation).
- Disk changes are not saved back to .dsk files.
- No tape support, so the CPC 464 runs BASIC only.
History
-------
0.8 Faster vertical scrolling (the display moves the picture in a
taller chip RAM buffer instead of redrawing it) and faster Plus
sprites. Sonic GX on a PiStorm: the slowdown on fast vertical
scrolls (springs) is now barely noticeable.
0.7 Much faster on full-screen scrolling games: only changed parts of
the screen are written to chip RAM, 5 or 6 bitplanes where 8 are
not needed, batched video emulation, table-driven Plus soft
scroll. Sonic GX: 41 -> 49 fps on an A1200 with PiStorm32, without
frame skip. New Arnold-030 build.
0.6 CPC 464/664/6128 and GX4000 models; Video mode (Auto/PAL/NTSC)
and Game speed in a new Settings box and Display menu; correct
50 Hz game and music speed on NTSC; menu fits 200 lines; screen
surround shows the CPC border colour; no Workbench flash.
0.5.2 Plus DMA interrupt fixes: Sonic GX's Green Hill split glitch and
its frozen special stage. The menu scrolls on NTSC displays.
0.5.1 First Aminet release.
Source and reports
------------------
Source, patches and issue tracker: https://github.com/z00p/arnold-amiga
Please report problems there with the game, your settings and your
machine.
Credits
-------
Arnold (c) Kevin Thacker, GPL-2.0. Amiga port by John Stringer, 2026.
CPCEC by CNGSoft was the accuracy reference for the Plus fixes.
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