1) Overview: how Sidekick64 plays SID music on a Plus/4

The Plus/4 doesn’t have a SID chip (it uses TED sound), so “SID music” normally isn’t possible without extra hardware. Sidekick64 (Sidekick264 mode) solves this by behaving like a SID expansion (“SID card”): Plus/4 software writes to SID registers at specific I/O addresses, and Sidekick emulates the SID and outputs audio.

Plain-English flow:
1) A Plus/4 SID player runs a tune and writes SID register values →
2) Those writes go to the SID-card address range →
3) Sidekick264 emulates the SID (e.g., using a reSID-style core) and produces the audio output.

Sidekick264 also supports other Plus/4-era “bonus” devices like FM-card emulation and Digiblaster output, but this page focuses on SID music.

2) SID card base addresses on Plus/4

The most important detail when playing/porting SID tunes is that Plus/4 SID cards do not normally live at $D400 (that’s the C64 SID base). On the Plus/4, the common SID card bases are:

Device Base address Notes
SID #1 (primary) $FD40 “Best bet” for remapping; widely supported by SID cards and software.
SID #2 (secondary / mirror) $FE80 Often supported as a second SID or mirror area, depending on the implementation.

Sidekick264 explicitly supports Dual-SID card emulation at $FD40 and $FE80.

Rule of thumb: If a tune or player is hardcoded for C64 $D400, it will likely need conversion or a SID-player that can target $FD40 (and optionally $FE80).

3) Requirements (hardware + power)

3.1 Hardware

  • Commodore Plus/4 (PAL or NTSC).
  • Sidekick64 + compatible Raspberry Pi for your Sidekick build.
  • The proper C16/+4 adapter / Sidekick264 hardware setup (the passive adapter setup is the typical path).
  • Audio output from your Sidekick setup (depends on your build/output method).

3.2 Power (important!)

Do NOT power the Sidekick64 from a C16/+4.
Sidekick64 documentation warns to always use an external power supply for these computers, and to avoid powering externally and from the computer at the same time.

4) Quick start: play SID music (minimal fuss)

If your goal is “browse a folder of SID tunes and play them”, the easiest workflow is usually to use a dedicated Plus/4 SID player that supports SID-card hardware (which Sidekick264 emulates).

  1. Enable Sidekick264 mode

    Make sure you are running the Sidekick264 build/config on your SD card and booting Sidekick in Plus/4 mode.

  2. Use a Plus/4 SID player (recommended)

    The SD2IEC SID Player is a known Plus/4 program designed to play SID files with an SD2IEC device and a SID card.

  3. Point it at your .SID collection

    Copy .SID files to your SD2IEC storage (or wherever your player reads from), run the player, select a tune, and play.

When this “just works”: Many PSID tunes play fine when the player handles loading and then writes SID registers to $FD40. If a tune fails, use the conversion workflows below.

5) Converting SID tunes for Plus/4 (Sidekick SID-card addresses)

Many SID tunes were written for the C64 and assume the SID base address $D400. On a Plus/4, you typically want the music code to write to $FD40 (and possibly $FE80). Below are proven approaches.

5.1 Method A — Use “Sid Converter” on the Plus/4 (classic)

Sid Converter is a Plus/4 utility whose stated purpose is: converting “usual C64 SID tunes ($D400) to SidCard working music ($FD40/$FE80).”

  1. Copy Sid Converter to your Plus/4 media

    Put the converter program where you can load it (disk/SD2IEC/etc.).

  2. Run Sid Converter

    Follow its prompts to convert/remap the tune so it targets $FD40/$FE80.

  3. Play the converted result

    Use a SID-card-aware player or run the converted executable (depending on output).

5.2 Method B — PC workflow: SID → PRG using psid64, then remap

PSID64 generates a C64 self-extracting executable (.PRG) from a .SID. A modern maintained CLI version exists on GitHub (handy on Windows/Linux/macOS). 

# Convert a SID into a runnable PRG (writes output.prg)
psid64 -o output.prg input.sid

After making a PRG, you still may need to remap SID access from $D400 to $FD40/$FE80 using Sid Converter or a Plus/4-aware player/toolchain.

5.3 Method C — Use PSID16 (SID → Plus/4 program)

PSID16 converts SID tunes into a C16/C232/Plus/4 program that plays the tune on a real (or emulated) Plus/4, but it still requires a SID card (which Sidekick264 provides).

Pick PSID16 when: you want a Plus/4-targeted output program rather than keeping everything in “C64 PRG” form.

6) Compatibility notes (why some tunes fail or sound different)

  • Address hardcoding: If the music routine writes to $D400, it won’t drive a Plus/4 SID card unless converted or the player supports remapping. (Community guidance generally says $FD40 is the “best bet”, with some support for $FE80 too.)
  • Timing / environment assumptions: Some tunes assume C64 IRQ/timer behavior, memory layout, or “RSID” constraints and may not behave on a Plus/4 environment.
  • Clock options (varies by SID hardware): Some SID-card hardware supports different clock modes (e.g., Plus/4 clock vs PAL C64 clock). If something sounds “off pitch”, clocking can be a reason—but exact behavior depends on the SID solution used.
If you want maximum compatibility, use a Plus/4 SID player designed for SID cards and treat conversion as “per-tune” when needed.

7) Troubleshooting

7.1 No sound at all

  • Confirm you’re actually in Sidekick264 mode (Plus/4 mode).
  • Confirm the player is SID-card aware and targets $FD40 (or $FE80).
  • Power: use an external PSU for Sidekick on Plus/4 (don’t power from the Plus/4).
  • Audio routing: verify your Sidekick output path (speaker/amp/jack) is correct.

7.2 Some SIDs play, some crash or hang

  • Try a different player (some handle more SID formats and edge cases).
  • Try conversion: Sid Converter (remap) or PSID16 (Plus/4-targeted output).
  • Prefer PSID over RSID when possible (RSID tends to be stricter about “real C64 behavior”).

7.3 Tune plays but sounds “wrong”

  • Check if the SID solution has clock options (some SID cards do). Different clocks can change pitch/feel.
  • Try a different SID emulation core/settings on the Sidekick side (if your build exposes that).

8) Sources & downloads

These references back the key details in this wiki (addresses, Sidekick264 capability, and conversion/player tooling). Replace/extend with your own preferred mirrors.

Suggested next addition: Add a “My Setup” section with your exact Sidekick hardware, Pi model, audio path, and the specific SID player you use. That’s usually what makes troubleshooting easy.