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Sidekick64 (C64 / C128 / C16/+4 / VIC-20)

Sidekick64 is a software-defined, Raspberry Pi powered cartridge/expansion that can emulate memory expansions, freezer cartridges, many cartridge formats, sound devices (multi-SID / SFX / MIDI), kernal replacements, function ROMs (C128), plus extras like audio playback and tools.

Official GitHub → Releases / downloads → BOM / iBOM (SK64) → BOM / iBOM (Zero 2 PCB) →
Note: This page is a friendly “cheat-sheet” like our RAD wiki. For authoritative details, always read upstream README + release notes (they change timings, images, and configs).

What it can emulate (big highlights)

  • GeoRAM/NeoRAM compatible memory expansion
  • Freezer cartridges: Action Replay 4–7, Final Cartridge 3(+), KCS Power Cartridge, Super Snapshot V5, Freeze Frame/Machine, Atomic/Nordic Power (experimental)
  • Cartridge formats: EasyFlash (simplified EAPI), GMOD2 (EEPROM save), MagicDesk/Domark/HES AU, Ocean A/B (up to 512k), Dinamic, C64GS, Comal80, Simons’ BASIC, Prophet64, RGCD/Hucky carts, etc.
  • C128: kernal replacement + Function ROMs, 2MHz reads supported in EasyFlash emu
  • Sound: up to 8 SIDs, SFX Sound Expander, FM emulation, MIDI (Datel/Sequential style) with SoundFont synth
  • Media/tools: handles PRG, D64, SID, MOD, YM, WAV; includes tools like Disk2EasyFlash and PSID64

Supported machines & Pi models

  • Machines: C64, C128, C16/+4, VIC-20 (via adapters)
  • Raspberry Pi: Pi 3A+, 3B+, and Zero 2 (Zero 2 is for C64/C128/VIC-20 use)
  • Tested: PAL + NTSC C64, C128/C128D, C16/+4 (PAL/PAL-N/NTSC), VIC-20 (PAL/NTSC), Ultimate64, C64 Reloaded
Power rule: Never power from the computer and external PSU at the same time. Never.

Quick start (SD card)

1) Get the firmware

Grab the latest release from GitHub, write/copy it to a FAT microSD (depending on the release format), then boot the Pi on the Sidekick64 PCB.

2) Configure

Main config lives at SD:C64/sidekick64.cfg. Set your display type (OLED or TFT), and choose how you want the menu to behave.

3) Add your content

  • Copy .CRT, .PRG, .D64, ROMs (.bin raw) into the folders used by the menu.
  • Optional: populate SD:/FAVORITES to auto-build a curated main menu (C64/C128).
  • You can customize splash screens and themes (see SD:SPLASH and display docs in the repo).
Safety tip (C64/C128, SID emu): if your real SID supports register reads, run SID+FM emulation with “register read” turned OFF in settings to reduce bus contention risk.

Build hardware (PCBs, BOM, assembly)

PCB variants

  • Large PCB fits Pi 3A+/3B+
  • Small PCB tailored for Pi Zero 2
  • Design intent: interchangeable (check revision notes upstream)

BOM / interactive BOM (iBOM)

Assembly order (simple)

  1. Solder SMD parts (top side only).
  2. Solder the 2×20 female header (Raspberry Pi socket).
  3. Solder pin headers + push buttons.
  4. Optional: attach SSD1306 OLED (4-pin) or ST7789 240×240 TFT (recommended).
Important jumper: external delay d=0..3. Use d=0 for C64/C128. Use d=3 for C16/+4 (Sidekick264 mode).

Extra wiring (only if you need SID CS / kernal replace)

For kernal replacement + SID emulation (C64/C128), upstream notes you may need wires from the Sidekick pins (“SID CS” / “CPU P1”) to CPU + SID socket (depends on machine).

Variants / modes

Variant Target What you get Notes
Sidekick64 C64 / C128 Menu, carts, freezers, memory, audio/SID/MIDI, tools, favorites Most common configuration.
Sidekick128 C128 PRG128 + CRT128 folders, function ROM emu, VDC output modes Can switch VIC/VDC output modes from menu (upstream feature).
Sidekick264 C16 / Plus-4 Menu + browser, PRG loading, cartridges (C1 low/high), sound options Requires adapter + d=3 jumper. Pi 3A+/3B+ preferred; heavy OC for Zero 2.
Sidekick20 VIC-20 VIC emulation via HDMI (optional), memory expansion emu, basic disk emu Requires adapter; VIC HDMI mode needs A15 wire from CPU to adapter “in 1”.

Sidekick264 (C16 / Plus-4) — the quick explainer

Sidekick264 is Sidekick64 running in the C16/+4 world using a passive adapter. You get the familiar menu + browser, plus PRG loading and cartridge support for that platform.

  • Enable it: in config.txt activate the include line for sidekick264_rpi3.txt (upstream naming).
  • Adapter: passive adapter between the machine port and Sidekick64.
  • Jumper: set delay jumper to d=3 for C16/+4 use.
  • Overclock: typically Pi 3A+/3B+ required; Zero 2 may need extreme OC and can be unstable.
Reset note: Plus/4 may require using the computer’s reset button rather than Sidekick’s reset, depending on setup.

Handy: PCBWay has shared adapter pages (if you want quick reference links): C16/+4 adapter • VIC-20 adapter

Powering & stability

Recommended: external PSU

Best practice is powering the Raspberry Pi externally, letting Sidekick boot to splash/menu, then turning on the Commodore.

Cartridge-port power (C64/C128 only)

Sidekick can be configured to draw from the expansion port via the “close to power…” jumper, but quality of the computer PSU matters. If anything is flaky, switch to a known-good external PSU first.

Absolute rule: NEVER power from computer and external PSU at the same time.

Building from source (for tinkerers)

Upstream builds are based on the Circle bare-metal environment (commonly referenced Circle 44.3 + gcc-arm setup). Different kernels can be built via make -kernel=... (menu, cart, sid, etc.), then copied with Pi firmware to a FAT SD.

If you’re doing this: stick closely to the build settings included in the repo.

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