Hitachi MB-H21
This page was last modified 14:43, 25 December 2021 by Gdx. Based on work by Mars2000you and Rderooy.




The Hitachi MB-H21 looks like a MB-H2 without its data recorder. It has a CPU speed controller switch, allowing slow games execution. The Cassette Operation Guide is replaced by a game: Roulette.

This model was aimed at the Japanese market. It has been localized for the Arabic countries - see Sakhr AH-200.

It was also planned to put the MB-H21 firmware in a model similar to the MB-H1, localized for Europe, but it has never been released - see MB-H80

Brand Hitachi
Model MB-H21
Year 1984
Region Japan
Launch price ¥49,800
RAM 32kB (? in slot 0)
Media MSX cartridges
Video Texas Instruments TMS9118NL
Audio PSG (AY-3-8910)
Chipset none (separate IC's)
Keyboard layout QWERTY/JP50on
Extras CPU speed controller switch, firmware (Sketch Program, Sound Play, Roulette, MB-H21 Monitor Program)
Emulation ROM dump needed. See this thread for details


The firmware available in this computer uses function keys F1 to F5:

  • F1 - MSX-BASIC (F1)
  • F2 - Sketch Program (graphic program)
  • F3 - Sound Play (music keyboard)
  • F4 - Roulette (game) and the
  • F5 - MB-H21 Monitor Program (disassembly/monitor of machine code)

There is no any key to bypass the firmware menu when booting because it is auto-bypassed when a ROM cartridge is inserted.

If you stay on the menu, an automatic demo of the Sketch-Sound options will begin after a few time.

When you have started an application, you can go back to the menu by entering E in the monitor or by pressing CTRL+STOP in the other applications.

From MSX-BASIC, you can

  • access to the command line of the Monitor with CALL MON or _MON (to get the list of all available commands in this utility, enter H on the command line - back to BASIC by entering E)
  • send a screendump of a text screen to a connected printer with CALL HCOPY or _HCOPY.



Hitachi MB-H21 with box
Hitachi MB-H21
Hitachi MB-H21 detail
Hitachi MB-H21 with manual
Hitachi MB-H21
Hitachi MB-H21 back
Hitachi MB-H21 label
Hitachi MB-H21 back connectors


Will be added later - the pictures should be similar to the Hitachi MB-H2 firmware, except for the Cassette Operation Guide, replaced by Roulette.


The MB-H21 is a MSX1 with a CPU speed controller for slow games execution. The CPU is a Z80A from Sharp (LH0080A).

The firmware is auto-bypassed when a cartridge is inserted in the slot 1 or 2 but it not working with a slot expander. To remedy this drawback, you have to insert a ROM cartridge in one of the two primary slots.

Slot Map

Help needed
This is the alleged slot map. We need confirmation because the RAM and firmware can be reversed.
Slot 0 Slot 1 Slot 2 Slot 3
Page C000h~FFFFh Cartridge
Slot 1
Slot 2
32kB RAM
Page 8000h~BFFFh Firmware
Page 4000h~7FFFh Main-ROM
Page 0000h~3FFFh