Yamaha CX5MII
This page was last modified 15:09, 16 December 2021 by Mars2000you. Based on work by Gdx and Rderooy and others.




The Yamaha computers were specifically targeted at music and sound production, and as such were regarded by many as non-standard MSX machines. However, they are in fact standard MSX1 computers and can be used as such.

The CX5MII is a Yamaha CX11 localised for the international market, but with more RAM and an additional ROM allowing to use the 80 column text mode.

The CX5MII is available in several models depending on the country of destination. The model version is marked only on the underside sticker. Almost all keyboards are QWERTY and include an accent key, but the version for France has an AZERTY layout. Only the CX5MIIE has a £ key. The variations are as follows:

Product Region Video Out Keyboard
CX5MIIA AU, NZ RF, RGB, Composite Audio and Video QWERTY
CX5MIIB IT RF, RGB, Composite Audio and Video QWERTY
CX5MIIC CA RF, Composite Audio and Video QWERTY
CX5MIIE UK RF, RGB, Composite Audio and Video QWERTY with £ key
CX5MIIG DE RF, Composite Audio and Video QWERTY
CX5MIIP ES RF, RGB, Composite Audio and Video QWERTY
CX5MIIS Scandinavia RF, Composite Audio and Video QWERTY
CX5MIIU US RF, Composite Audio and Video QWERTY

Brand Yamaha
Model CX5MII or CX5MII/128
Year 1985
Region Australia, Canada, France, Germany, Italy, New Zealand, Scandinavia, Spain, United Kingdom, United States
Launch price
RAM 64kB (CX5MII) or 128kB (CX5MII/128) in slot 3-2
Media MSX cartridges, side slot modules
Video Yamaha V9938 (MSX2 VDP!)
Audio PSG (YM2149 integrated in MSX-Engine S3527), SFG-05, MIDI
Chipset Yamaha S3527
Keyboard layout (France) AZERTY - (Other countries) QWERTY with variations
Extras 60 pin module port, mini cartridge port, FM module SFG-05, YRM-502 FM Voicing Program II, internal RAM / VRAM expandable
Emulation ROMs dumped and emulated for both types, but only two models. The mini-cartridge slot and module slot are handled like regular MSX cartridge slots. ROM dumps needed for the other versions. See this thread for details


This computer was sold with a FM module SFG-05 plugged into side slot. From BASIC, the synthesizer can be launched with CALL MUSIC or _MUSIC.

It has also a mini cartridge YRM-502 FM Voicing Program II plugged into mini slot. From BASIC, this sound editor can be started with CALL FMV or _FMV. Contrary to the first version of this software, only available as cartridge (YRM-102), this second version has support for loading from/saving to disk.

When you are in the sound editor, you can go to the synthesizer by entering MU. To go back to the FM Voicing Program, you need to press ESC in the synthesizer firmware.



Yamaha CX5MII
Yamaha CX5MII French
Yamaha CX5MII/128
Yamaha CX5MII left side
Yamaha CX5MIIA/B/E/P back
Yamaha CX5MII right side
Yamaha CX5MII Mainboard
Yamaha CX5MII VRAM Board
Yamaha CX5MII RAM Board
Yamaha CX5MIIF inside
Yamaha CX5MII/128 inside
Yamaha CX5MII/128 RAM Board
Yamaha CX5MII/128 box
Yamaha CX5MII/128 label


SFG-05 Polyphonic mode (F2)
SFG-05 Monophonic mode (F1)
SFG-05 Voice menu (F3)
SFG-05 Load/Save menu (F4)


YRM-502 Command menu
YRM-502 Edit mode (F1)
YRM-502 Directory (DI)
YRM-502 Edit key list (F5)
YRM-502 Command key list (F5)
YRM-502 Load/Save menu (TR)
YRM-502 Common key list (F5)


The CX5MII is a MSX1 with a Z80A from Sharp (LH0080A), a V9938 and an MSX-Engine S3527 from Yamaha. The CX5MII is available in two models. One with 64kB RAM and one with 128kB RAM, what's very rare on MSX1!

This model can be easily upgraded internally (except the CX5MIIG and CX5MIIS versions, respectively for the German and Scandinavian markets), because RAM and VRAM are each on separate boards with a connector, you just need to change the corresponding board.

Some machines don't have a separate VRAM board but you can change the VRAM on the mainboard.

The mini slot allows to add software.

Slot Map

Slot 0 Slot 1 Slot 2 Slot 3-0 Slot 3-1 Slot 3-2 Slot 3-3
Page C000h~FFFFh Cartridge
Slot 1
Slot 2
64 or
Page 8000h~BFFFh
Page 4000h~7FFFh Main-ROM Sub-ROM
Page 0000h~3FFFh
  • The second part of the 16kB Sub-ROM used by openMSX is empty (value FFh), the active part is mapped from 4000~5FFFh and corresponds to a 8kB ROM
  • By default the Mini-Cartridge slot contains a FM Voicing Program II cartridge (YRM-502) from 4000~7FFFh
  • By default the Module Slot contains a SFG-05 module from 0000~7FFFh



  • CX5MIIA: Australian and New Zealand's market (RF = PAL-B on VHF 3/4ch)
  • CX5MIIB: Italian market (RF = PAL-G on UHF 36ch)
  • CX5MIIC: Canadian market (RF= NTSC on VHF 3/4ch)
  • CX5MIIE: United Kingdom's market (RF = PAL-I on UHF 36ch)
  • CX5MIIF: French market (only RGB output)
  • CX5MIIG: German market (RF = PAL-G on UHF 36ch)
  • CX5MIIP: Spanish market (RF = PAL-G on UHF 36ch)
  • CX5MIIS: Scandinavian market (RF = PAL-G on UHF 36ch)
  • CX5MIIU: United States market (RF = NTSC on VHF 3/4ch)