Yamaha YIS-503II
This page was last modified 23:28, 16 December 2021 by Mars2000you. Based on work by Gdx and Rderooy and others.



The YIS-503II is the successor to the YIS-503, and is same as the CX5MII but sold without any side module.

The YIS-503II was aimed at the Japanese market and features a Japanese keyboard. It looks like the CX11 but has more RAM and was sold without any module.

System sets

Just like with its predecessor, the YIS-503, it was also offered as a set

  • YIS-503GII Graphic System for ¥80,400, consisting of:
  • YIS-503MII Music System for ¥117,200, consisting of:
  • YIS-503WII Word Processing System for ¥194,400, consisting of:
    • YIS-503II
    • SKW-01 Kanji Word Processor Unit
    • PN-01 thermal printer
    • CB-01 printer cable

Localised editions

This model has been localised and modified to be

  • sold in Arabic countries - see Sakhr AX-200 - without the not usable mini-slot
  • used in schools of Soviet Union - see YIS-503IIR.
Brand Yamaha
Model YIS-503II
Year 1985
Region Japan
Launch price ¥59,800
RAM 64kB in slot 3-2
Media MSX cartridges, side slot modules
Video Yamaha V9938 (MSX2 VDP!)
Audio PSG (YM2149 integrated in MSX-Engine S3527), (Music System package) SFG, MIDI
Chipset Yamaha S3527
Keyboard layout QWERTY/JP50on
Extras 60 pin module port, internal RAM / VRAM expandable, Graphic System, Music System and Word Processing System packages
Emulation ROM dumped and emulated. The side module slot is handled like a regular MSX cartridge slot.


Yamaha YIS-503II
Yamaha YIS-503II label
Yamaha YIS-503II box + content
Yamaha YIS-503II left side
Yamaha YIS-503II back
Yamaha YIS-503II right side
Yamaha YIS-503II PCB
Yamaha YIS-503II underside (with empty module slot)
Yamaha YIS-503II with box


The YIS-503II is a MSX1 with a Z80A from Sharp (LH0080A), a V9938 and an MSX-Engine S3527 from Yamaha.

This computer supports all Yamaha modules. It can be easily upgraded internally because RAM and VRAM are each on separate boards with a connector, you just need to change the corresponding board..

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
Page 8000h~BFFFh
Page 4000h~7FFFh Main-ROM
Page 0000h~3FFFh