Panasoft FM-PAC
This page was last modified 15:37, 5 January 2017 by Rderooy. Based on work by Mars2000you and Gdx.



The FM-PAC is an FM sound synthesizer cartridge which was originally made by Panasonic. The full name is FM Pana Amusement Cartridge and the product ID is SW-M004. It's the only official cartridge version of the MSX-MUSIC standard. It was released under the Panasoft brand, used by Panasonic for a few software.

This cartridge contains the MSX-MUSIC chip with its specific BIOS - see MSX-MUSIC BASIC, and a SRAM for saving game states (compatible with PAC).

A switch allows to choose between 3 possible output volumes for the MSX-MUSIC sound, which is mono.

The cartridge also has a built-in software, which can be started by running CALL FMPAC or _FMPAC from BASIC. Here you can listen to various demo sounds, and backup and restore the SRAM content. In the BGM (Back Ground Music) menu option you can press TAB to get a music keyboard to play something yourself.

Hardware Gallery

Panasoft FM-PAC Cartridge scan
Panasonic FM-PAC complete package
Panasonic FM-PAC cartridge
SW-M004 PCB front with removed button cell
SW-M004 PCB front
SW-M004 PCB back

Software Gallery

Main Menu
Option 1: Clear
Option 2: Copy
Option 3: Change
Option 4: Delete file
Option 5: Slot
Option 6: BGM
Music keyboard


  • YM2413 FM chip
  • 16kB MSX-MUSIC Basic
  • 4kB SRAM (just like the Panasonic SW-M001 PAC)
  • Volume adjuster
  • Mono sound output
  • Built-in firmware

See MSX-MUSIC page for more specifications.


The FM-PAC (and likewise the Panasoft PAC) has a battery, without it the SRAM will not keep the contents when the system is switched off. This coin cell battery can be replaced, you need to open the cartridge and replace the battery with a new one (type: Panasonic BR2325 Lithium 3V). See this thread for details.

Typically a PAC compatible game will have one of these logo's on the box. They may also indicate which save slots they need.

PAC Logo
PAC Logo
PAC Logo, indicating the game needs slot 8
PAC Logo, indicating the game needs slot 1-4

External links