Yamaha YIS-805
This page was last modified 15:49, 20 January 2023 by Mars2000you. Based on work by Rderooy and Gdx and others.




The Yamaha YIS-805 comes with a separate keyboard and in 2 versions:

  • The /128 version has only 128kB RAM and 1 disk drive by default, but there's a location planned for the addition of a second disk drive
  • The /256 version has 256kB RAM, 2 disk drives and a RS-232C interface

Both versions have an expansion bus at the back, reserved for a digitizer, also known as 'video enhancer'.

It's the last computer released by Yamaha for the MSX system and the only one with a built-in floppy drive. It has still a special slot for specific Yamaha modules.

The Yamaha YIS-805 was advertised to be used with the following software and extensions:

  • FM Sound Synthesizer Unit Ⅱ SFG-05 ¥ 29,800
  • FM Voicing Program II YRM-55 ¥ 9,800
  • Phrase Conversion Cartridge YRK-50 ¥ 24,800
  • Captain Adapter Unit SCA-01 ¥ 40,000
  • Captain Modem Unit MD-01 ¥ 98,000
  • EFD-10 Second disk drive for the YIS-805/128 ¥ 40,000

The YIS-805/128 has been localised for the Russian market - see YIS-805/128R2 - without the expansion bus slot.

The YIS-805/256 has been localised for the Arabic countries - see Sakhr AX-500 - without the expansion bus slot and the RS-232C interface.

Brand Yamaha
Model YIS-805/128 or YIS-805/256
Year 1986-06-21
Region Japan
Launch price ¥148,000 for the YIS-805/128
¥198,000 for the YIS-805/256
RAM 128kB or 256kB (? in slot 3-2) + 2kB SRAM
VRAM 128kB
Media MSX cartridges, 2DD floppy disks
Video Yamaha V9938
Audio PSG (YM2149 integrated in MSX-Engine S1985)
Chipset Yamaha S1985
Keyboard layout QWERTY/JIS + numeric keypad
Extras 1 or 2 720kB 3,5" floppy disk drives, reset button, 60 pin module port, Kanji Word Processor Unit SKW-05 with Kanji-ROM Level 1, THE PAINTER (graphic tool), 2DD disk with YIS-805 Set Up Program and MSX-DOS 1, (only /256 version) RS-232C interface + RS-232C BASIC
Emulation /128 version: several ROMs dumped but machine not yet emulated. /256 version: ROM dumps required. Both versions: SKW-05 ROMs, module and system disk dumps needed. See this thread for details


This machine comes with

  • the firmware THE PAINTER, a graphic utility in screen 5 (64kB ROM) that can be launched with CALL PAINT or _PAINT, but you can also boot the computer while pressing the SPACE key to directly start this utility.
  • the firmware Kanji Word Processor Unit SKW-05 that includes
    • a 48kB ROM with the application that can be launched with CALL JWP or _JWP
    • a 32kB ROM with a Kanji Dictionary
    • a 2kB SRAM
    • a non-standard 128kB Kanji-ROM (JIS1) with 3979 characters
    • a switch at the top with the indication "MEMORY POWER" (probably to enable/disable the SRAM)


This machine was provided with a floppy disk with YIS-805 Set Up Program and MSX-DOS 1



Yamaha YIS-805/256 box
Yamaha YIS-805/128
Yamaha YIS-805 underside
Yamaha YIS-805 manuals
Yamaha YIS-805/256 front
YIS-805/256 front (closeup)
Yamaha YIS-805/128 back
Yamaha YIS-805/256 back
Yamaha YIS-805 keyboard
Yamaha YIS-805 right side


The Painter
The Painter


The YIS-805 is a MSX2 with a Z80A from Sharp (LH0080A) and an MSX-Engine S1985 from Yamaha. This computer is available in two models. One with 128kB RAM and one with 256kB RAM.

The /128 version can be easily upgraded internally to 256kB RAM.

The floppy disk controller chip is the 8876.

Slot Map

Help needed
The below slot-map is an assumption, it needs to be checked on a real machine.
Slot Slot
0-0 0‑1 0-2 0-3 Slot 1 Slot 2 3-0 3-1 3-2 3-3
Page C000h~FFFFh Expansion
Slot 1
Slot 2
Page 8000h~BFFFh
Page 4000h~7FFFh Main-ROM RS-232C
Disk ROM
Page 0000h~3FFFh Sub-ROM
  • By default the Module Slot contains the Kanji Word Processor Unit SKW-05
  • The RS-232C ROM is a 8KB ROM - 4000h-5FFFh - it is not present on the YIS-805/128 model
  • In the Russian version of YIS805/128, slot 0 is not expanded. The RS-232C ROM is not present, but in the side slot there is the special "network" module to communicate with students' computers that have similar modules - see YIS-805/128R2