Description

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:

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).

Pictures

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

Specifications

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

Connections

• RF output
• Analog sound (stereo on Japanese version) & Composite video
• (only Japanese version and optional) slot for the HX-R701 optional RS-232C connector
• Data Recorder connector
• Centronics compatible Parallel port for a printer
• 2 general connectors (Joysticks, Mouse, Paddle controlers, etc)
• 2 cartridge slots
• Power plug male for main power supply (JIS C 8303 class, AC 100V +/-10% 50/60Hz)

External links

• Blog post about the HX-20AR (Korean)