pSOS (Portable Software On Silicon) is a

real-time operating system A real-time operating system (RTOS) is an operating system (OS) for real-time computing applications that processes data and events that have critically defined time constraints. A RTOS is distinct from a time-sharing operating system, such as Unix ...

(RTOS), created in about 1982 by Alfred Chao, and developed and 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 system An embedded system is a specialized computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is e ...

s based on the

Motorola 68000 series The Motorola 68000 series (also known as 680x0, m68000, m68k, or 68k) is a family of 32-bit computing, 32-bit complex instruction set computer (CISC) microprocessors. During the 1980s and early 1990s, they were popular in personal computers and ...

family architecture, because it was written in 68000

assembly language In computing, assembly language (alternatively assembler language or symbolic machine code), often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence bet ...

and was highly optimised from the start. It was also modularised, with early support for OS-aware debugging, plug-in

device driver In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabli ...

Internet protocol suite The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...

(TCP/IP) stacks, language

libraries A library is a collection of Book, books, and possibly other Document, materials and Media (communication), media, that is accessible for use by its members and members of allied institutions. Libraries provide physical (hard copies) or electron ...

, and disk subsystems. Later came

source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...

level debugging,

multiprocessing Multiprocessing (MP) is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. The ...

support, and further

computer network A computer network is a collection of communicating computers and other devices, such as printers and smart phones. In order to communicate, the computers and devices must be connected by wired media like copper cables, optical fibers, or b ...

ing extensions. In about 1991, Software Components Group was acquired by Integrated Systems Inc. (ISI) which further developed pSOS, then renamed as pSOS+, for other microprocessor families, by rewriting most of it in the

programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...

C. Attention was also paid to supporting successively more

integrated development environment An integrated development environment (IDE) is a Application software, software application that provides comprehensive facilities for software development. An IDE normally consists of at least a source-code editor, build automation tools, an ...

s, culminating in pRISM+. In July 1994, ISI acquired

Digital Research Digital Research, Inc. (DR or DRI) was a privately held American software company created by Gary Kildall to market and develop his CP/M operating system and related 8-bit, 16-bit and 32-bit systems like MP/M, Concurrent DOS, FlexOS, Multiuser ...

's modular real-time multi-tasking operating system

FlexOS FlexOS is a discontinued modular real-time multiuser multitasking operating system ( RTOS) designed for computer-integrated manufacturing, laboratory, retail and financial markets. Developed by Digital Research's Flexible Automation Business ...

from

Novell Novell, Inc. () was an American software and services company headquartered in Provo, Utah, that existed from 1980 until 2014. Its most significant product was the multi-platform network operating system known as NetWare. Novell technolog ...

. In 1995, ISI offered a pSOSystem/NEST package for

Novell Embedded Systems Technology Novell Embedded Systems Technology (NEST) was a series of application programming interface, APIs, data formats and network protocol stacks written in a highly portable fashion intended to be used in embedded systems. The idea was to allow vario ...

(NEST). In February 2000, ISI was acquired by

Wind River Systems Wind River Systems, Inc., also known as Wind River (trademarked as Wndrvr), is an Alameda, California–based company, subsidiary of Aptiv PLC. The company develops embedded system and cloud software consisting of real-time operating systems sof ...

, the originators of the rival RTOS

VxWorks VxWorks is a real-time operating system (or RTOS) developed as proprietary software by Wind River Systems, a subsidiary of Aptiv. First released in 1987, VxWorks is designed for use in embedded systems requiring real-time, Deterministic system, ...

. Despite initial reports that pSOS support would continue, development was halted. Wind River announced plans for a 'convergence' version of VxWorks which will support pSOS system calls, and that no further releases of pSOS will occur.

NXP Semiconductors NXP Semiconductors N.V. is a Dutch semiconductor manufacturing and design company with headquarters in Eindhoven, Netherlands. It is the third largest European semiconductor company by market capitalization as of 2024. The company employs approx ...

acquired pSOS for TriMedia from Wind River and continued to support this OS for the TriMedia

very long instruction word Very long instruction word (VLIW) refers to instruction set architectures that are designed to exploit instruction-level parallelism (ILP). A VLIW processor allows programs to explicitly specify instructions to execute in parallel, whereas conve ...

(VLIW) core.

Migration away from pSOS

In March 2000, rival company Express Logic released their Evaluation Kit for pSOS+ users, designed to provide a migration path to its ThreadX RTOS. During August 2000, MapuSoft Technologies Inc. came up with the pSOS OS Changer porting kit which can smoothly move the software to multiple OS such as

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

, VxWorks, and more. It includes an ''

'' (IDE) and ''application programming interface'' (

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

) optimization along with a profiling tool to measure API timing on target boards (www.mapusoft.com). In August 2007, RoweBots, a former partner of SCG and ISI,

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

d their pSOS+ compatible version called Reliant. It is available to all that wish to upgrade without application changes. The

Xenomai Xenomai is a software framework cooperating with the Linux kernel to provide interface-agnostic, hard real-time computing support to user space application software seamlessly integrated into the Linux environment. The Xenomai project was launch ...

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 Linux-based environment while keeping stringent real-time guarantees. Another open sourced alternative is

RTEMS Real-Time Executive for Multiprocessor Systems (RTEMS), formerly Real-Time Executive for Missile Systems, and then Real-Time Executive for Military Systems, is a real-time operating system (RTOS) designed for embedded systems. It is free and open ...

, which has support for various APIs, including the "Classic API" (compatible to pSOS) and the POSIX API. Compared to Linux, RTEMS is a closer match to pSOS applications due to its lower memory size and its strict realtime behaviour. Popular ''Secure Sockets Layer'' (SSL), now ''

Transport Layer Security Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network, such as the Internet. The protocol is widely used in applications such as email, instant messaging, and voice over ...

'' (TLS), libraries such as

wolfSSL wolfSSL is a small, portable, embedded SSL/TLS library targeted for use by embedded systems developers. It is an open source implementation of TLS (SSL 3.0, TLS 1.0, 1.1, 1.2, 1.3, and DTLS 1.0, 1.2, and 1.3) written in the C programming langu ...

still support pSOS.

Migration away from pSOS

See also

References

Further reading