Skip to content

Commodore Plus/4

Commodore Plus4 icon Commodore Plus4 logo

Overview

The Commodore Plus/4 (C16/Plus/4 family) is a productivity-focused 8-bit computer released in 1984. It ships with built-in office programs (Word Writer, Spreadsheet, etc.) and a MOS 7501/8501 CPU, but retains partial compatibility with Commodore 64 titles. REG-Linux treats it as part of the c64 group while offering the cplus4 artwork set where available.

Technical specifications

  • CPU: MOS 7501/8501 at 1.77 MHz (6502-derived)
  • Memory: 64 KB RAM plus 96 KB ROM space for bundled software
  • Graphics: VIC-II compatible for 320×200/16-color output
  • Sound: TED chip with three square-wave channels and DAC output

Supported ROM extensions

d64, prg, tap, m3u, zip, 7z

Quick reference

  • Emulators: VICE (xplus4), libretro: vice_xplus4
  • ROM folder: /userdata/roms/cplus4
  • Accepted formats: .d64, .prg, .tap, .m3u, .zip, .7z

BIOS

No additional BIOS files are required for Plus/4 emulation; VICE ships with everything needed.

ROMs

Store Plus/4 disk, cartridge and tape images in /userdata/roms/cplus4. Use raw images or zipped collections depending on your preference.

Emulators

VICE (xplus4)

The standalone xplus4 emulator targets the Plus/4, C16 and related machines. REG-Linux surfaces standardized options such as cplus4.videomode, cplus4.padtokeyboard, cplus4.ratio, cplus4.bezel, cplus4.hud, etc.

ES setting name REG-Linux.conf_key Description => ES option key_value
ZOOM (HIDE BORDERS) cplus4.noborder Hide the overscan border (useful when games draw HUD elements in it). => NO (default) 0, YES 1.

RetroArch (libretro: vice_xplus4)

libretro: vice_xplus4 runs Plus/4 content inside RetroArch. Settings are available via the Quick Menu ([HOTKEY] + south button) and include global options (cplus4.videomode, cplus4.shaderset) plus vice core keys.

ES setting name REG-Linux.conf_key Description => ES option key_value
GRAPHICS API cplus4.gfxbackend Choose OpenGL or Vulkan.
AUDIO LATENCY cplus4.audio_latency Adjust buffer size to fix pops.
ALLOW ROTATION cplus4.video_allow_rotate Permit rotated output from the core.
CONTROLLER TO LIGHT GUN cplus4.lightgun_map Map buttons to gun inputs when needed.
MODEL TYPE global.plus4_model Lock to a specific machine variant (PLUS4 PAL/NTSC, C16, etc.).
COLOR FILTER global.vice_plus4_external_palette Override the color palette.
ASPECT RATIO global.vice_aspect_ratio Set the output ratio (PAL vs NTSC).
ZOOM MODE global.vice_zoom_mode Manage border cropping.
BUTTON OPTIONS global.vice_retropad_options Customize face button behaviour.
CONTROLLER PORT global.vice_joyport Force joystick port 1 or 2.
CONTROLLER TYPE global.vice_joyport_type Choose joystick/paddle/mouse.
KEYBOARD PASS-THROUGH global.vice_keyboard_pass_through Pass physical keyboard events to the core.

Controls

The default Plus/4 layout maps to the REG-Linux Retropad. Use VICE or RetroArch’s input configuration for title-specific adjustments.

Commodore Plus/4 controller overlay

Troubleshooting

  • Switch joystick ports if input feels wrong (global.vice_joyport).
  • Toggle the zoom/border option if the game draws HUD elements in the border area.