Bit^2 MIDI-Saurus
This page was last modified 12:31, 7 December 2021 by Mars2000you. Based on work by Gdx and Rderooy and others.



The Bit² BM-012 is an external MIDI interface for MSX2 and higher which came with MIDI-Saurus. The interface has three connectors on top of it: MIDI-IN, MIDI-OUT and MIDI-THRU (2nd MIDI-OUT). It has its own Z80A microprocessor, timer and memory capable to playback MIDI on the slower MSX2/2+ as well. This way the MIDI interface takes care of all incoming MIDI-commands and the computer can do other things at the same time.

Programming information was published in the MSX-Magazine Issue 1990/07, page-77 and Issue 1990/08, page-59, but this documentation is still only available in Japanese. It's confirmed that the interface works at port 70H-73H. Ports 71H and 73H are command ports and ports 70H and 72H are data ports. It was only sold in Japan and a few were imported to Europe. It's rare nowadays.

For games it's known Famicle Parodic 2 has support for this interface, but there could be some more.

Here's a video which shows how the MIDI-Saurus can perform. In the video it uses μ-Note.


  • Dump MIDI controller ROM v1.00
  • MIDRY option /I0 or /I01 for MIDI-OUT 1 or option /I02 for MIDI-OUT 2 (MSX2/2+/MSX turbo R: Z80 mode) - also support for ReComPoser MIDI files (.RCP) The only MIDI player as known for MIDI Saurus

<Unconfirmed data found by looking at ROM dump>
ROM is mapped in external Z80 address space to #0000-#1FFF and 8KB SRAM is mapped to #E000-#FFFF. External Z80 is uses I/O ports #10-13 and #18-#1F to communicate to outside world. ie. I/O port #1C is linked to MSX I/O port #71
</Unconfirmed data found by looking at ROM dump>


Bit² MIDI-Saurus cartridge
Bit² MIDI-Saurus package
Bit² MIDI-Saurus PCB