pSOS

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pSOS
Company/
developer		 Alfred Chao / SCG / ISI / Wind River Systems
Programmed in 68000 assembler
OS family Real-time operating systems
Source model Closed source
Initial release 1982
Marketing target Embedded systems
Supported platforms Motorola 68000
Kernel type Real-time
License Proprietary
Working state Discontinued

According to some industry insiders, pSOS stands for plug-in Silicon Operating System but the official stance is that it is not an abbreviation, just a made-up word. (The original authors will not divulge the origin of the term.)

This real time operating system (RTOS) was created in about 1982 by Alfred Chao, and developed/marketed for the first part of its life by his company Software Components Group (SCG). In the 1980s pSOS rapidly became the RTOS of choice for all embedded systems based on the Motorola 68000 family architecture, because it was written in 68000 assembler and was highly optimised from the start. It was also modularised, with early support for OS-aware debugging, plug-in device drivers, TCP/IP stacks, language libraries and disk subsystems. Later came source-level debugging, multi-processor support and further networking extensions.

In about 1991, Software Components Group was acquired by Integrated Systems Inc. (ISI) who further developed pSOS - now restyled pSOS+ - for other microprocessor families, by rewriting the greater part of it in C. Attention was also paid to supporting successively more integrated development environments, culminating in pRISM+.

In 1999 Integrated Systems Inc. 'merged with' (in reality they were taken over by) Wind River Systems, the originators of rival RTOS VxWorks. Despite initial reports that pSOS support would continue, development has been halted. Due in the near future is a 'convergence' version of VxWorks which will support pSOS system calls, and it has been announced that no further releases of pSOS itself will be made.

NXP Semiconductors acquired pSOS for TriMedia from Wind River and continues to support this OS for the TriMedia VLIW core.

[edit] Migration away from pSOS

In March 2000, rival company Express Logic released their Evacuation Kit for pSOS+ users, designed to provide a migration path to its ThreadX RTOS.

In August 2007, RoweBots, a former partner of SCG and ISI, open sourced their pSOS+ compatible version called Reliant. It is available to all that wish to upgrade without applications changes.

The Xenomai project supports pSOS+ APIs (and others traditional RTOS APIs) over a Linux-based real-time framework to allow existing industrial applications to migrate easily to a GNU/Linux-based environment while keeping stringent real-time guarantees.

[edit] External links