Psion Organiser II Technical Details and Trivia


  • a "topslot" expansion slot for fitting the Psion Printer, barcode reader, external power supply or other devices - 16-pin female socket
  • two datapack slots underneath - for programs, extra storage, etc.
  • 9V PP3-type battery connector

Technical Facts

  • The top slot (3) and two side slots (1 and 2) are pin-compatible, sharing a single bus. As a result it is entirely possible to connect peripherals to the side slots rather than the top slot, although the top slot is physically designed to support connectors with wires more easily.
  • The Hitachi 6301 (or 6303) CPU used in the Organiser 1 (or II, respectively) is actually a re-implementation of the Motorola MC6801, a member of the very popular 6800 family of CPUs. It is object code-compatible with the Motorola CPU, and is bus-compatible with the 6800.
  • The Organiser 1 used the Hitachi HD6301X MPU (Micro Processing Unit), whereas the Organiser II used the Hitachi HD6303X MPU. The 6301 MPUs contains a CPU, 4 bytes of ROM, 192 bytes of RAM, 53 parallel I/O pins, a Serial Communication Interface (SCI) and two timers on a single chip. The 6303 differs in that it contains only 24 parallel I/O pins. Both are built on the CMOS fabrication process.
  • The Organiser 1 used a "linear addressing" method to access data on Datapaks, which leads to slow access times on larger packs. For the Series II a faster addressing method was devised, namely "paged addressing".
  • Flashpaks contain EEPROM chips. These can be formatted electronically by the organiser. All it needed was a software driver that is normally present on the flashpak itself. In order to restore the driver software to the pak after formatting, a second pack with a copy of the driver was needed in the other slot. Flashpaks came in the sizes 128K and 256K.


Hover your mouse over the circuit board for a description of the components



  • On the Organiser 1, you could only get DataPaks in 8K and 16K sizes, although rumour has it 32K datapaks were available.
  • The Organiser II can use Organiser 1 datapaks, but actually the Datapaks available (branded) for the Organiser II have a revised circuitry to allow any pack size to use the same PCB.
  • The following Datapaks were available for the Organiser II: 8K, 16K, 32K, 64K and 128K.
  • When reformatting Datapaks, Psion's instructions were to remove the label which reveals a small opening over the EPROM chip. The formatter then shines UV light into this hole, destroying (clearing) the data from the Datapak. It takes about half an hour to complete the format. These days it's recommended to open the Datapak up to reveal the entire circuit, just so you don't end up spoiling the sticker!
  • The Oxford Concise Spelling Checker pack used the same circuitry as a 64K Datapak, but it used a 64K PROM chip instead of an EPROM.
  • The Thesaurus and Spelling Checker travel pack had unique circuitry with a surface-mounted 256K ROM chip. This used different addressing methods to other packs, but its software allows it to be used on any Organiser, even the CM.
  • Psion only produced Rampaks in 32K size. Other third parties produced compatible packs with other sizes, including Dynasys and MSE Data.


This page was last updated on 17th November 2015.