Category:Toshiba HX-20
This page was last modified 13:54, 17 November 2022 by MSX Calamar. Based on work by Mars2000you and Gdx and others.



The HX-20 was a modulable computer released by Toshiba in Japan. It is the second revision released to replace the previous HX-10 series. This computer was sold in three versions (HX-20, HX-21 and HX-22). This one is the "standard version", i.e. without RGB output nor RS-232C.

The HX-20 was exported to several countries with following references:

Product Region Keyboard Video and audio out Other
HX-20 JP QWERTY/JIS RF, composite video and stereo audio Optional RS-232C interface
HX-20AR AR QWERTY with accent key RF, composite video and mono audio
HX-20E ES QWERTY with accent key (no ñ!) RF, composite video and mono audio
HX-20I IT QWERTY with accent key RF, composite video and mono audio

An RS-232C interface with its switch can be added on the Japanese model by soldering the connector on the power supply board, the same RS-232C board from the HX-22. You also need to add a connector on the power supply board or or solder the wires directly. You can also do it on other models by replacing the IC3 ROM with the one from the HX-22CH, HX-22GB or HX-22I.

A kit was sold for the HX-20 and HX-21 by Toshiba in Japan at the time. This is the HX-R701 kit. It can also be used on the HX-23, HX-23F and HX-32.

The RGB output can also be added on the Japanese model (and probably on the HX-20E and HX-20I models) by soldering several components as on the video decoder board from the HX-22.

Although it's a MSX1 computer, it can use a part of the MSX memory to create a Memory Disk (feature generally reserved for MSX2 and higher computers).

Brand Toshiba
Model HX-20 / HX-20AR / HX-20E / HX-20I
Year 1984-10-16 in Japan - 1985 in Spain - 1986 in Argentina
Region Argentina, Italy, Japan, Spain
Launch price ¥69,800
RAM 64kB split between slots 0 and 3-0
Media MSX cartridges
Video TMS9128 (HX-20, HX-20AR) or Toshiba T6950 (other models)
Audio PSG (AY-3-8910A)
Chipset Toshiba TCX-1010 or Toshiba TCX-1012
Keyboard layout see table above
Extras firmware (Japanese Word Processor - Kanji-Kun v.2.0 or English Word Processor), MemoryDisk BASIC, (only Japanese version) Printer BASIC, stereo PSG sound and RS-232C BASIC, (only Japanese version and optional) Toshiba HX-R701 RS-232C interface + switch
Emulation HX-20E dumped and emulated. ROM dump needed for the other versions. See this thread for details


Check also the pages about the different models!

Toshiba HX-20
Toshiba HX-20AR
Toshiba HX-20AR inside
Toshiba HX-20E
Toshiba HX-20E PCB
Toshiba HX-20I
Toshiba HX-20 back
Toshiba HX-20I right side
Toshiba HX-20I back


The HX-20 is a MSX1 with 2 cartridge slots (one at the top, one at the back) and a a Z80A from Sharp (LH-0080A).

The 2 joystick ports are located on the right side of the computer, as well as the data recorder connector.

The used VDP is most versions of this computer is the Toshiba T6950, which does not support some undocumented features of the Texas Instruments TMS9918, TMS9928 and TMS9929 VDP's.

The 64kB RAM is split between slots 0 and 3-0, a configuration that can cause poorly written software to crash. Also, with this layout, the POKE-1,(15-PEEK(-1)\16)*17 trick to workaround buggy software that does not handle subslots properly will not work on this machine.

Slot Map

Slot 0 Slot 1 Slot 2 Slot 3-0 Slot 3-1 Slot 3-2 Slot 3-3
Page C000h~FFFFh Upper
32kB RAM
Slot 1
Slot 2
Page 8000h~BFFFh Firmware
Page 4000h~7FFFh Main-ROM Lower
32kB RAM
Page 0000h~3FFFh


External links

Pages in category "Toshiba HX-20"

The following 4 pages are in this category, out of 4 total.