Yamaha YIS-503
This page was last modified 23:25, 16 December 2021 by Mars2000you. Based on work by Rderooy and Gdx and others.



The YIS-503 is same as the CX5F but sold without any module. The color is different.

It was aimed at the Japanese market and features a Japanese keyboard. The power supply is internal.

System sets

It was also offered in packages with other Yamaha hardware:

  • YIS-503G Graphic System, for ¥85,700 consisting of:
  • YIS-503M Music System, for ¥115,500, consisting of:
    • YIS-503
    • YK-10 Music Keyboard
    • SFG-01 FM Sound Synthesizer Unit
    • VC-01 video cable
  • YIS-503W Word Processing System, for ¥210,500, consisting of:

Localised editions

The YIS-503 has been adapted for the French and Belgian markets - see Yamaha YIS-503F - and for the Arabic countries - see Sakhr AX-100.

Brand Yamaha
Model YIS-503
Year 1984
Region Japan
Launch price ¥64,800
RAM 32kB in slot 0
Media MSX cartridges, side slot modules
Video Texas Instruments TMS9928A
Audio PSG (YM2149), (Music System package) SFG, MIDI
Chipset Yamaha YM5214
Keyboard layout QWERTY/JP50on
Extras 60 pin module port, Graphic System, Music System and Word Processing System packages
Emulation ROM dumped and machine emulated. The rear expansion slot and side module slot are handled like regular MSX cartridge slots.


YIS-503 box + content
Yamaha YIS-503
Yamaha YIS-503 underside
Yamaha YIS-503 PCB
Yamaha YIS-503 with box
Yamaha YIS-503 left side
Yamaha YIS-503 back
Yamaha YIS-503 right side
Yamaha YIS-503 box
Yamaha YIS-503 manuals
Yamaha YIS-503 label


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

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

To get 64kB RAM with the YIS-503, 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. As such it is recommended to use a 64kB expansion, or a MSX1 compatible MemoryMapper that can self-initialise.

Slot Map

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