Configuration
It had several innovative features:
- Twin 720kB 3.5" diskette drives
- Wireless infra-red keyboard
- 16-color monitor
- Stackable expansion
In Japan both white and black units were available, but elsewhere all IBM JX's were black—very unusual in the days of the standard color of IBM "beige boxes".
However, it shared many of the disadvantages of the IBM PCjr:
- Could not the use the standard ISA bus cards of the PC XT
- Would not run software written to directly address hardware (such as Microsoft Flight Simulator)
The system operated PC-DOS 2.11 as well as, Microsoft disk BASIC and Advanced BASIC. Like the IBM PC, if the system was left to boot without inserting a diskette into one of the drives the Microsoft Cassette BASIC interpreter would be loaded, which was compatible with IBM PCjr BASIC, including Cartridge BASIC. PC-DOS 2.11 could only use half of the tracks of a 3.5" drive, however, since it didn't really understand what a 3.5" drive even was. The PCjx's BIOS could only address the first 40 tracks like a 5.25" drive.
The PCjx later had a BIOS upgrade chip, sold together with DOS 3.21, which permitted the full 720kB capacity of the diskette drives to be used. Some popular options for the PCjx were a 10MB external hard disk (as a stackable unit the same size as the JX itself) and a joystick. IBM never released a 3270 emulation adapter for the PCjx in order to steer enterprise customers to more expensive IBM PCs and XTs.
Read more about this topic: IBM JX