Yamaha CX11
This page was last modified 23:22, 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 MSX computers and can be used as such.

The CX11 was aimed at the Japanese market and features a Japanese keyboard. It has 32kB RAM just like the CX5F, but the back expansion bus is replaced by a second top cartridge slot.

Contrary to what the casing suggests (see the bottom), this machine does not have a mini-slot and there isn't even the place on the mainboard to solder it.

Brand Yamaha
Model CX11
Year 1985
Region Japan
Launch price ¥54,800
RAM 32kB (in slot 0)
Media MSX cartridges, side slot modules
Video Yamaha V9938 (MSX2 VDP!)
Audio PSG (YM2149 integrated in MSX-Engine X3527), SFG, MIDI
Chipset Yamaha X3527 (a previous version of the Yamaha S3527)
Keyboard layout QWERTY/JP50on
Extras 60 pin module port, FM module SFG-01
Emulation ROMs dumped and emulated. The side module slot is handled like a regular MSX cartridge slot.


This machine was sold with a FM synthesizer module SFG-01 plugged into the side slot with MIDI IN and OUT. There is also an updated version called the SFG-05, sold separately. From BASIC, the music firmware can be launched with CALL MUSIC or _MUSIC.



Yamaha CX11
Yamaha CX11 box
Yamaha CX11 inside
Yamaha CX11 PCB
Yamaha CX11 PCB detail
Yamaha CX11 - X3527 MSX-Engine
Yamaha CX11 left side
Yamaha CX11 right side
Yamaha CX11 underside
Yamaha CX11 back
Yamaha CX11 manuals
Yamaha CX11 label


SFG-01 Screen

More info about the SFG modules on these pages:


The CX11 is a MSX1 with a Z80A from Sharp (LH0080A), a V9938 (MSX2) VDP and a MSX-Engine X3527 (previous version of S3527) from Yamaha.

To get 64kB RAM, you can insert the URM-01 cartridge in slot 1 or 2 or the SRE-01 module in side slot 3. It means that the 64kB RAM is split between two slots, a configuration that can cause poorly written software to crash. Also, with this layout, the POKE-1,(15-PEEK(-1)\16)*17 trick to workaround buggy software that does not handle subslots properly will not work on this machine expanded to 64kB RAM.

This model can be easily upgraded to MSX2 as the internal components are already present. Of course, you need to add more RAM and VRAM.

Slot Map

Slot 0 Slot 1 Slot 2 Slot 3
Page C000h~FFFFh RAM Cartridge
Slot 1
Slot 2
Page 8000h~BFFFh
Page 4000h~7FFFh Main-ROM
Page 0000h~3FFFh
  • By default the Module slot contains a SFG-01 from 4000-7FFF (which gets mirrored to 0000-3FFF and 8000-FFFF)