PSOS

pSOS stands for plug-in Silicon Operating System. 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. In the 1980s 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. 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.