IBM JX

The IBM JX (or JXPC) is an IBM 5511 personal computer released in 1984 into the Australian and Japan markets. It was marketed as the next generation of the IBM PCjr, though fell short as it was unable to use standard ISA bus cards such as could be used in a PC XT. It did run standard DOS software, or even bootable PC software such as Microsoft Flight Simulator. The JX was much more successful in the Australian and Japanese markets than the PCjr was in the United States.

Notable features include 2x 720kB 3.5" drives, wireless infra-red keyboard, and a 16-colour monitor.

The system operated PC-DOS 2.11 and Advanced BASIC. If the system was left to boot without inserting a diskette into one of the drives the 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 pretended to be 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 and a joystick. IBM never released any kind of 3270 emulation adapter for the PCjx in order to steer enterprise customers to more expensive PCs and PC XTs.