Yamaha YIS-303
This page was last modified 13:30, 20 April 2018 by Rderooy. Based on work by Mars2000you and Gdx and others.



The computer YIS-303 is a bridled CX5. This model was sold without any module, the printer port and half of the RAM are missing. The color is also different.

It was aimed at the Japanese market and features a simple Japanese keyboard with 70 keys. The power supply is internal.

Official price: ¥49,800

Brand Yamaha
Type YIS-303
Year 1983-11
RAM 16kB (in slot 0)
Media MSX cartridges, side slot modules
Video Texas Instruments TMS9918A
Audio PSG (YM2149)
Chipset Yamaha YM5214


Yamaha YIS-303 box and content
Yamaha YIS-303 PCB
Yamaha YIS-303 missing printer port
Yamaha YIS-303


The YIS-303 supports all Yamaha modules, but not the module HC-A602S from Victor. The Video processor is not a TMS9928A.

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

The printer port is missing but we can add it by soldering a connector and the four chips near the cartridge connector on PCB. We can also add 16KB by soldering 4416 x2 and two 74LS244 instead the straps in the chip locations near at right.

Slot Map

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


  • DIN 41524 Monitor output
  • Tape recorder connector
  • 2 general connectors (joysticks, mouse, paddle controllers, ...)
  • 1 cartridge slot
  • 1 module slot (left side, 60 pin connector without signals need for superimpose)
  • 1 expansion bus slot (back side, 2nd cartridge slot via CA-01 adapter)

External links