Yamaha YIS-805/128R2
This page was last modified 23:42, 16 December 2021 by Mars2000you. Based on work by Gdx and Rderooy.




The Yamaha YIS-805/128R2 is the adaptation of the YIS-805/128 computer for Soviet Union. It has by default one disk drive, but there's a location planned for the addition of a second disk drive. The expansion bus slot at the back has been removed.

This machine was not sold in shops and could only be used in schools. The "КУВТ2" logo is the abbreviation of "Комплект учебной вычислительной техники 2" and means "Class of Teaching Computing Equipment 2". According to a Japanese MSX Magazine article (issue 1989-03), 4000 units were exported to the Soviet Union.

This computer has a Russian keyboard, it was generally used by the teacher while the students had a YIS-503IIIR without any drive. The communication between MSX computers is actually controlled by a sophisticasted interface called Serial I/O Unit Mk II.

This interface has 2 specific serial ports and an internal DIP switch with 4 configurable bits that define the number of student machine (1 - 15). Setting DIP to 0 makes the machine a teacher's machine.

In this MSX-Network, up to 8 student machines are connected to a teacher machine using one of the floppy disk drives for centralised file storage.

Note: This communication system is completely incompatible with the system used on the MSX1 YIS-503IIR computer.

Brand Yamaha
Model YIS-805/128R2
Year 1986
Region USSR
Launch price
RAM 128kB in slot 3-2
VRAM 128kB
Media MSX cartridges, DD floppy disks
Video Yamaha V9938
Audio PSG (YM2149 integrated in MSX-Engine S1985)
Chipset Yamaha S1985
Keyboard layout JCUKEN/Cyrillic + numeric keypad
Extras 1 or 2 720kB 3,5" floppy disk drives, reset button, 60 pin module port, Network unit + switch + Network BASIC, THE PAINTER (graphic tool)
Emulation ROMs dumped and emulated, with exception of the Serial I/O network device


When booting, the network is automatically initialized, you can switch it off by CALL NETEND or _NETE and eventually switch it on again with CALL NETINIT or _NETI (all CALL commands can be shortened to 3-4 letters and a space is not required after the underscore).

The network firmware can be disabled by pressing DEL key while booting. It is recommended to disable it for playing games, this to avoid eventual incompatibility or for using the machine as a standard MSX2. However, some games were adapted to play them in network.

Another firmware is included in this computer, it's THE PAINTER, a graphic utility in screen 5. From MSX-BASIC, this firmware 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.



Yamaha YIS/805-128R2
Yamaha YIS/805-128R2 keyboard
Yamaha YIS/805-128R2
Yamaha YIS/805-128R2 front
Yamaha YIS/805-128R2 PCB
Yamaha YIS/805-128R2 back
Yamaha YIS/805-128R2 right side
Yamaha Serial I/O Unit Mk II connectors


The Painter
The Painter


The YIS-805/128R2 is a MSX2 with a Z80A from Sharp (LH0080A) and an MSX-Engine S1985 from Yamaha. Floppy Disk Controller chip is the 8876.

This model can be easily upgraded internally to 256kB RAM.

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 Disk ROM
Page 0000h~3FFFh Sub-ROM
  • By default the Module Slot contains a serial network interface module from 4000-BFFF