The REX 6000 is an ultra-thin Personal Digital Assistant (PDA) produced by Xircom, and later Intel, from about 2000 to 2001.
[1] In addition, it is possible to remove and install executable code (including both custom applications and the operating system itself).
As with the earlier models, the REX 6000 hardware was developed by the Citizen Watch Company of Japan, marketed as the "DataSlim-2".
(Earlier REXes stored user data in RAM with the operating system in ROM.)
It uses a 4.3 MHz Toshiba microprocessor compatible to the Zilog Z80, has a 240 × 120 pixel monochrome LCD, and is capable of providing beep sounds to deliver alarms and reminders.