This page was last modified 21:31, 7 March 2018 by Mars2000you. Based on work by Sd snatcher.

The MSX-BIOS is the software heart of the MSX system. Unlike other competing computer standards where the BIOS was just meant to initialize the computer and boot the operating system, the MSX-BIOS is meant as a real hardware abstraction layer to keep a consistent interface for user programs regardless of the hardware differences underneath.

It's composed of the mandatory main module and many optional complementary modules for specific functions. The specification allows new modules to be created and added as needed. Those modules are:


Original BIOS set

Mandatory main modules

  • Main BIOS
  • SubROM (only for MSX2 or higher)

Optional complementary modules

  • DiskBIOS
  • MSX-JE

Complementary BIOS modules created by the MSX community

  • Ethernet BIOS

Each module is designed to contain the drivers for the respective device and act as an hardware abstraction layer for user programs to use. They’ll also provide:

  • Standardized BIOS functions
  • Device independence
  • Instant plug and play with zero user intervention
  • Optional: Hooks for further extensibility
  • Optional: BASIC extension commands
  • Optional: CALL commands
  • Optional: Extended BIOS API functions

Optionally, a device cartridge ROM that contain the BIOS can also contain other built-in software, like:

  • Dedicated tools (either on boot or activated with the CALL command. I.e.: CALL FMPAC, CALL SYNTHE, CALL COMTERM)
  • MSX-DOS2 kernel (with or without built-in disk drivers)
  • Samples

The system is so powerful and flexible that it’s even possible to replace the built-in Main BIOS with an external cartridge. The Neos MA-20 "version up adapter" does exactly that.