PSOS (real-time operating system)

pSOS stands for plug-in Silicon Operating System. This 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. In the 1980's pSOS rapidly became the RTOS of choice for all embedded systems based on 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 SNiFF+.

In 1999 Integrated Systems Inc. 'merged with' (in reality they were taken over by) Wind River Systems, the originators of rival RTOS VxWorks, who had previously acquired a number of other providers in the embedded systems arena, including compiler maker Microtec Research (MRI). Despite initial reports that pSOS support would continue, the writing is on the wall. Due in the near future is a 'convergance' version of VxWorks which will support pSOS system calls. It remains to be seen whether the venerable and once-unbeatable pSOS (which still has a number of powerful advantages over its rivals) can survive these political and commercial pressures, and in what form it may do so.