Psion Organiser - Organiser I

Organiser I

The Psion Organiser I model, launched in 1984 was the "World's First Practical Pocket Computer". Based on an 8-bit Hitachi 6301-family processor, running at 0.9MHz, with 4kB of ROM and 2kB of static RAM, and had a single-row monochrome LCD screen. The size in mm with the case closed is 142 x 78 x 29.3, and the weight is 225 grams.

The machine provided a simple flat-file database, calculator and clock, and had no operating system. The Organiser I supported removable storage write-once devices which used EPROM storage. The machine could host two of these so-called DATAPAKs (or simply PAKs), to which it could write data but which needed to be removed from the machine and erased by being exposed to ultraviolet light before they could be re-used. As Psion had patented the use of EPROMS as storage device it was impossible for other device manufacturers to copy this innovative approach to mobile storage.

Software supplied on DATAPAK included a crude programming language called POPL, in which end-users could write their own programs. Software DATAPAKs titled Science, Maths and Finance contained the POPL programming language editor, interpreter and runtime and extended the built-in calculator by adding named functions. These DATAPAKs also contained different sets of application programs written in the POPL language.

A far more sophisticated programming tool was later made available with the implementation of the Forth programming language, but was available to registered professional developers rather than end users. The Psion Forth Development System for the Organiser I was a powerful set of IBM PC-based cross-development tools for producing Forth application programs, including a Forth compiler. The Forth system on the Organiser I itself had a compiler to intermediate code, interpreter and runtime, and had a number of unusual design features one being that it could interpret - that is, read and execute - Forth intermediate code directly in place on a DATAPAK, rather than needing to copy it into precious RAM first, despite the DATAPAKs not being execute-in-place memory-mapped.

Software developed by Psion as part of the Organiser I project and application software after its launch was written in 6301 assembler language, in POPL, and in other custom-designed languages. Assembler language development at Psion itself was carried out using cross-development tools, including a cross assembler and linker, all of which ran on a DEC VAX.

Application developers writing in 6301 assembler struggled with the small amount of RAM (2k), and the lack of an operating system. Another difficulty for developers was with the performance limitations of the earliest DATAPAKs which used a serial-access internal architecture, as opposed to random access. Retrieving for example byte 2000 from a DATAPAK meant issuing successive hardware commands to either step from the current read position one address place at time until position 2000 was reached or in the worst case resetting the read position to zero and then issuing a step-forward command 2000 times.

The Hitachi 6301 processor is an enhanced development based on the Motorola 6801 implemented in CMOS, with a number of extra instructions, various hardware system-on-single chip facilities on-chip, power management and support for a sleep state. The particular variant chosen also had 4KiB of masked ROM on-chip, so an external ROM was not needed on the board.

Having fully static RAM and a processor whose clock could be frozen without losing state meant spectacular battery life, measured in weeks or even months. Minimal battery consumption was aided by the processor being frozen whenever there was no work to do, plus a deeper sleep mode which turned off the display.

The machine lacked a full independently battery-backed, date-time real-time hardware clock, instead it had a simple hardware counter. While the machine was sleeping, the counter counted 1024 seconds and then woke the machine very briefly so that software could add 1024 seconds to a record of the time held in RAM. This meant that when sleeping the machine woke very, very fleetingly every 17m 4s.

The original 1984 price was £99 (GBP) and $199 (CAD) and included one Datapak and one software DATAPAK, the "Utility" pack. This latter adds scientific and trigonometric functions to the otherwise basic calculator routines.