Yamaha YIS-503F
This page was last modified 09:35, 20 March 2022 by Mars2000you. Based on work by Gdx and Rderooy and others.



The Yamaha CX5, CX5F, CX5M, CX5MII and CX5MII/128 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 YIS-503F is same as the CX5M but sold without any module. The color is gray and silver. The power supply is the external NP 55170. It is heavy and big. It's the adaptation for the French market of the YIS-503.

There is another model called YIS-503FB. It is indicated only on the label. It has a PAL-G output instead of RGB and the SRE-01 32kB memory expansion. This model was sold in Belgium.

Brand Yamaha
Model YIS-503F / YIS-503FB
Year 1984
Region Belgium and France
Launch price
RAM 32kB in slot 0 (YIS-503F) or 64kB split between slots 0 and 3-1 (YIS-503FB)
Media MSX cartridges, side slot modules
Video Texas Instruments TMS9929A
Audio PSG (YM2149)
Chipset Yamaha YM5214
Keyboard layout QWERTY with a "£" key
Extras 60 pin module port
Emulation ROM dumped and emulated. The rear expansion slot and side module slot are handled like regular MSX cartridge slots.


Yamaha YIS-503F box
Yamaha YIS-503F
Yamaha YIS-503F with PSU
Yamaha YIS-503F with box and manuals
Yamaha YIS-503F back
Yamaha YIS-503FB back
Yamaha YIS-503F underside
Yamaha YIS-503FB label
Yamaha YIS-503F monitor connector


The YIS-503F is a MSX1 with a Z80A from Sharp (LH-0080A). It supports all Yamaha modules ("units").

To use the expansion bus as second cartridge slot, you need the Yamaha Single Cartridge Adapter CA-01.

To get 64kB RAM with the YIS-503F, you can insert the URM-01 cartridge in slot 1 or 2 or the SRE-01 module in side slot 3. The SRE-01 module expands slot 3: slot 3-1 becomes an extra cartridge slot and slot 3-0 hosts the extra RAM.

In all cases the additionnal RAM is placed at addresses 0000h~7FFFh. 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. The same problems exist also on the variant YIS-503FB.

Slot Map of model YIS-503F

Slot 0 Slot 1 Slot 2 Slot 3
Page C000h~FFFFh RAM Cartridge
Page 8000h~BFFFh
Page 4000h~7FFFh Main-ROM
Page 0000h~3FFFh

Slot Map of model YIS-503FB

Slot 0 Slot 1 Slot 2 Slot 3-0 Slot 3-1 Slot 3-2 Slot 3-3
Page C000h~FFFFh Upper
32kB RAM
Slot 1
Slot 2
Page 8000h~BFFFh
Page 4000h~7FFFh Main-ROM Lower
32 kB RAM
Page 0000h~3FFFh