OS-9
Encyclopedia
OS-9 is a family of real-time
, process-based
, multitasking
, multi-user
, Unix-like
operating system
s, developed in the 1980s, originally by Microware Systems Corporation
for the Motorola 6809
microprocessor
. It is currently owned by RadiSys Corporation.
The OS-9 family was popular for general-purpose computing and remains in use in commercial embedded system
s and amongst hobbyists. Today, OS-9 is a product name used by both a Motorola 68000
-series machine language OS and a portable (PowerPC
, x86, etc.) version written in C
, originally known as OS-9000.
for the Motorola 6809
CPU, and provided a single 64 KB address space in which all processes ran. It was developed as a supporting operating system for the BASIC09
project, contracted for by Motorola as part of the 6809 development. A later 6809 version ("Level Two") takes advantage of memory mapping hardware, supported up to 2 MB of memory (ca 1980) in most implementations, and included a GUI
on some platforms.
In 1983, OS-9/6809 was ported to Motorola 68000
assembly language and extended (called OS-9/68K); and a still later (1989) version was rewritten mostly in C
for further portability. The portable version was initially called OS-9000 and was released for 80386
PC systems around 1989, then ported to PowerPC
around 1995. These later versions lack the memory mapping
facilities of OS-9/6809 Level Two simply because they do not need them. They used a single flat address space that all processes share; memory mapping hardware, if present, is mostly used to ensure that processes access only that memory they have the right to access. The 680x0 and 80386
(and later) MPUs
all directly support far more than of memory in any case.
As a consequence of early pervasive design decisions taking advantage of the easily used reentrant object code capabilities of the 6809 processor, programs intended for OS-9 are required to be reentrant; compilers produce reentrant code automatically and assemblers for OS-9 offer considerable support for it. OS-9 also uses position independent code and data because the 6809 also supported it directly; compilers and assemblers supported position independence. The OS-9 kernel loads programs (including shared code), and allocates data, wherever sufficient free space is available in the memory map. This allows the entire OS and all applications to be placed in ROM or Flash memory, and eases memory management requirements when programs are loaded into RAM and run. Programs, device drivers, and I/O managers under OS-9 are all 'modules' and can be dynamically loaded and unloaded (subject to link counts) as needed.
OS-9/6809 ran on Motorola
EXORbus systems using the Motorola 6809
, SS-50 Bus
and SS-50C bus systems from companies such as SWTPC
, Tano, Gimix, Midwest Scientific, and Smoke Signal Broadcasting, STD-bus 6809 systems from several suppliers, personal computers such as the Fujitsu
FM-11, FM-8
, FM-7
and FM-77, Hitachi
MB-S1, and many others.
System Industries, a third-party provider of DEC compatible equipment, used a 68B09E processor running OS9 in its QIC (quarter inch cartridge) tape backup controllers in VAX installations.
The best known hardware (due to its low price and broad distribution) was the TRS-80 Color Computer
(CoCo) and its clones such as the British Dragon
series. Even on the CoCo, a quite minimalist hardware platform, it was possible under OS-9/6809 Level One to have more than one interactive user running concurrently (for example, one on the console keyboard, another in the background, and perhaps a third interactively via a serial connection) as well as several other non-interactive processes. A second processor implementation for the BBC Micro
was produced by Cumana. It included on-board RAM, SASI hard disk interface and a MC68008 processor.
On a computer like an SS-50, machines which had more memory (for example, those from Gimix, Southwest Technical Products, etc.), and I/O controllers that did not load the CPU as did the CoCo, multiple users were common, even with only 64 KB of RAM (i.e., Level One). With hardware supporting memory management circuits (that is, address translation) and OS-9 Level 2, GUI
use was successfully routine, even on the minimal resourced CoCo. This was several years prior to successful GUIs on the 16-bit IBM PC class machines, and many years prior to properly working multi-tasking, multi-user, access-controlled operating systems on IBM PC type machines or on any of Apple's machines.
OS-9's multi-user and multi-tasking capabilities make it usable as a general-purpose interactive computer system. Many third-party interactive applications have been written for it, such as the Dynacalc spreadsheet
, the VED text formatter, and the Stylograph and Screditor-3 WYSIWYG
word processor
s. TSC
's nroff
emulating formatter was ported to OS-9 by MicroWay, as well.
In mid 1980s, OS-9 was selected for the CD-i
operating system. Around the same time, Microsoft
approached Microware for acquisition of the company primarily because it was attracted by CD-RTOS, the CD-i operating system. The negotiation failed and no deal was made; Microware decided to remain independent.
In late 1980s, Microware released OS-9000, a more portable version of the operating system. The vast majority of the operating system kernel was rewritten in C
leaving a handful of hardware-dependent parts in assembly language. A few "more advanced features" were added such as tree-like kernel module name space. OS-9000 was initially ported to the Motorola 680x0 family CPUs, Intel 80386
, and PowerPC
. The OS-9000/680x0 was a marketing failure and withdrawn very quickly, probably because few customers wanted to try the fatter and slower operating system over the existing OS-9/680x0 proven record of stability. That the Motorola 680x0 family and VME
board computer system vendors were nearing their end of life might have affected the unpopularity of OS-9000/680x0. Microware later started calling all of its operating systems — including what had been originally called OS-9000 — simply OS-9, and started shifting its business interest towards portable consumer device markets such as cellphones, car navigation, and multimedia.
In late 1980s and early 1990s, the Character Generators computers used in Broadcast Systems used OS-9 and OS-9000 extensively. The now defunct Pesa Electronica used OS-9 on their CGs such as CG 4722 and CG4733.
released Mac OS 9
. Microware sued Apple that year for trademark infringement, although a judge ruled that there would be little chance for confusion between the two. Some Macintosh users who are unaware of Microware's relatively unknown OS-9 have posted to the news://comp.os.os9 newsgroup; not realising what OS-9 is.
In 2000, RadiSys purchased Microware to acquire the Intel IXP-1200 network processor resources. This acquisition infused Microware with capital and allowed Microware to continue OS-9 development and support. As of 2011, OS-9 is still supported by RadiSys and Microware.
When compared with more modern operating systems.
is not a single tree, but instead is a forest with each tree corresponding to a device. Second, OS-9 does not have a Unix-style fork
system call—instead it has a system call which creates a process running a specified program, performing much the same function as a fork-exec
or a spawn
. Additionally, OS-9 processes keep track of two "current directories" rather than just one; the "current execution directory" is where it will by default look first to load programs to run (which is of course similar to the use of PATH environment variable
under UNIX). The other is the current data directory. OS-9 has had a modular design from the beginning, influenced by notions of the designers of the 6809
and how they expected software would be distributed in the future (see the three-part series of articles in Jan-Mar 1979 Byte by Terry Ritter, et al. of Motorola who designed the CPU).
OS-9/non-68000 supports POSIX threads. A single process can start any number of threads.
This rivalry went far enough that the OS-9 version 2.4 manual had this entry describing UNIX
in the Glossary of Appendix C of "Using Professional OS-9":
UNIX:
An operating system similar to OS-9, but with less functionality and
special features designed to soak up excess memory, disk space and CPU
time on large, expensive computers.
This entry was removed in the version 3.0 manual.
The OS-9 shell had an easter egg in its command history
function, invoked by CTRL-A. Upon a fresh boot, the command history was supposedly empty, but if the user typed a single space followed by a backspace, then hit CTRL-A, the names of the authors would be displayed: 'by K. Kaplan, L. Crane, R. Doggett'.
Real-time computing
In computer science, real-time computing , or reactive computing, is the study of hardware and software systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response. Real-time programs must guarantee response within strict time constraints...
, process-based
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
, multitasking
Computer multitasking
In computing, multitasking is a method where multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for...
, multi-user
Multi-user
Multi-user is a term that defines an operating system or application software that allows concurrent access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving the...
, Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s, developed in the 1980s, originally by Microware Systems Corporation
Microware
Microware is a US corporation that produced the OS-9 real-time operating system.Microware Systems Corporation existed as a separate entity from 1977 until September 2001, when it was bought by RadiSys Corp., and became a division of that company...
for the Motorola 6809
Motorola 6809
The Motorola 6809 is an 8-bit microprocessor CPU from Motorola, designed by Terry Ritter and Joel Boney and introduced 1978...
microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
. It is currently owned by RadiSys Corporation.
The OS-9 family was popular for general-purpose computing and remains in use in commercial embedded system
Embedded system
An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
s and amongst hobbyists. Today, OS-9 is a product name used by both a Motorola 68000
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
-series machine language OS and a portable (PowerPC
PowerPC
PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
, x86, etc.) version written in C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, originally known as OS-9000.
History
The first version ("OS-9 Level One"), which dates back to 1979–80, was written in assembly languageAssembly language
An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
for the Motorola 6809
Motorola 6809
The Motorola 6809 is an 8-bit microprocessor CPU from Motorola, designed by Terry Ritter and Joel Boney and introduced 1978...
CPU, and provided a single 64 KB address space in which all processes ran. It was developed as a supporting operating system for the BASIC09
BASIC09
BASIC09 is a structured BASIC programming language dialect developed by Microware for the then-new Motorola 6809 CPU. Somewhat in the fashion of UCSD Pascal it was implemented via 'compilation' into an intermediate representation...
project, contracted for by Motorola as part of the 6809 development. A later 6809 version ("Level Two") takes advantage of memory mapping hardware, supported up to 2 MB of memory (ca 1980) in most implementations, and included a GUI
Gui
Gui or guee is a generic term to refer to grilled dishes in Korean cuisine. These most commonly have meat or fish as their primary ingredient, but may in some cases also comprise grilled vegetables or other vegetarian ingredients. The term derives from the verb, "gupda" in Korean, which literally...
on some platforms.
In 1983, OS-9/6809 was ported to Motorola 68000
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
assembly language and extended (called OS-9/68K); and a still later (1989) version was rewritten mostly in C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
for further portability. The portable version was initially called OS-9000 and was released for 80386
Intel 80386
The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...
PC systems around 1989, then ported to PowerPC
PowerPC
PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
around 1995. These later versions lack the memory mapping
Memory management
Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and freeing it for reuse when no longer needed. This is critical to the computer system.Several...
facilities of OS-9/6809 Level Two simply because they do not need them. They used a single flat address space that all processes share; memory mapping hardware, if present, is mostly used to ensure that processes access only that memory they have the right to access. The 680x0 and 80386
Intel 80386
The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...
(and later) MPUs
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
all directly support far more than of memory in any case.
As a consequence of early pervasive design decisions taking advantage of the easily used reentrant object code capabilities of the 6809 processor, programs intended for OS-9 are required to be reentrant; compilers produce reentrant code automatically and assemblers for OS-9 offer considerable support for it. OS-9 also uses position independent code and data because the 6809 also supported it directly; compilers and assemblers supported position independence. The OS-9 kernel loads programs (including shared code), and allocates data, wherever sufficient free space is available in the memory map. This allows the entire OS and all applications to be placed in ROM or Flash memory, and eases memory management requirements when programs are loaded into RAM and run. Programs, device drivers, and I/O managers under OS-9 are all 'modules' and can be dynamically loaded and unloaded (subject to link counts) as needed.
OS-9/6809 ran on Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
EXORbus systems using the Motorola 6809
Motorola 6809
The Motorola 6809 is an 8-bit microprocessor CPU from Motorola, designed by Terry Ritter and Joel Boney and introduced 1978...
, SS-50 Bus
SS-50 Bus
The SS-50 bus was an early computer bus designed as a part of the SWTPC 6800 Computer System that used the Motorola 6800 CPU. The SS-50 motherboard would have around seven 50-pin connectors for CPU and memory boards plus eight 30-pin connectors for I/O boards...
and SS-50C bus systems from companies such as SWTPC
SWTPC
The U.S. company SWTPC started in 1964 as DEMCO . It was incorporated in 1967 as Southwest Technical Products Corporation of San Antonio, Texas...
, Tano, Gimix, Midwest Scientific, and Smoke Signal Broadcasting, STD-bus 6809 systems from several suppliers, personal computers such as the Fujitsu
Fujitsu
is a Japanese multinational information technology equipment and services company headquartered in Tokyo, Japan. It is the world's third-largest IT services provider measured by revenues....
FM-11, FM-8
FM-8
The FM-8 was a personal computer developed and manufactured by Fujitsu in May 1981. It was Fujitsu's second microcomputer released to the public after the LKIT-8 kit computer, and the first in the "FM" series. The FM-8 would later be replaced by two new models in November 1982 - the FM-11, aimed...
, FM-7
FM-7
FM-7 is a home computer released in 1982 in Japan.The Fujitsu FM-7 was Fujitsu's first entry into the Japanese home computer market, and for their debut computer, they chose to come out with a 6809-based personal computer very similar to Radio Shack's Color Computer.-Hardware:*Two MC 68B09 CPUs @...
and FM-77, Hitachi
Hitachi
Hitachi is a multinational corporation specializing in high-technology.Hitachi may also refer to:*Hitachi, Ibaraki, Japan*Hitachi province, former province of Japan*Prince Hitachi and Princess Hitachi, members of the Japanese imperial family...
MB-S1, and many others.
System Industries, a third-party provider of DEC compatible equipment, used a 68B09E processor running OS9 in its QIC (quarter inch cartridge) tape backup controllers in VAX installations.
The best known hardware (due to its low price and broad distribution) was the TRS-80 Color Computer
TRS-80 Color Computer
The Radio Shack TRS-80 Color Computer was a home computer launched in 1980. It was one of the earliest of the first generation of computers marketed for home use in English-speaking markets...
(CoCo) and its clones such as the British Dragon
Dragon 32/64
The Dragon 32 and Dragon 64 are home computers that were built in the 1980s. The Dragons are very similar to the TRS-80 Color Computer , and were produced for the European market by Dragon Data, Ltd., in Port Talbot, Wales, and for the US market by Tano of New Orleans, Louisiana...
series. Even on the CoCo, a quite minimalist hardware platform, it was possible under OS-9/6809 Level One to have more than one interactive user running concurrently (for example, one on the console keyboard, another in the background, and perhaps a third interactively via a serial connection) as well as several other non-interactive processes. A second processor implementation for the BBC Micro
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
was produced by Cumana. It included on-board RAM, SASI hard disk interface and a MC68008 processor.
On a computer like an SS-50, machines which had more memory (for example, those from Gimix, Southwest Technical Products, etc.), and I/O controllers that did not load the CPU as did the CoCo, multiple users were common, even with only 64 KB of RAM (i.e., Level One). With hardware supporting memory management circuits (that is, address translation) and OS-9 Level 2, GUI
Gui
Gui or guee is a generic term to refer to grilled dishes in Korean cuisine. These most commonly have meat or fish as their primary ingredient, but may in some cases also comprise grilled vegetables or other vegetarian ingredients. The term derives from the verb, "gupda" in Korean, which literally...
use was successfully routine, even on the minimal resourced CoCo. This was several years prior to successful GUIs on the 16-bit IBM PC class machines, and many years prior to properly working multi-tasking, multi-user, access-controlled operating systems on IBM PC type machines or on any of Apple's machines.
OS-9's multi-user and multi-tasking capabilities make it usable as a general-purpose interactive computer system. Many third-party interactive applications have been written for it, such as the Dynacalc spreadsheet
Spreadsheet
A spreadsheet is a computer application that simulates a paper accounting worksheet. It displays multiple cells usually in a two-dimensional matrix or grid consisting of rows and columns. Each cell contains alphanumeric text, numeric values or formulas...
, the VED text formatter, and the Stylograph and Screditor-3 WYSIWYG
WYSIWYG
WYSIWYG is an acronym for What You See Is What You Get. The term is used in computing to describe a system in which content displayed onscreen during editing appears in a form closely corresponding to its appearance when printed or displayed as a finished product...
word processor
Word processor
A word processor is a computer application used for the production of any sort of printable material....
s. TSC
Technical Systems Consultants
Technical Systems Consultants was a US software company.Headquartered first in West Lafayette, Indiana and later moved to Chapel Hill, North Carolina, it was the foremost supplier of software for SWTPC compatible hardware, as well as many other early makes of personal computers...
's nroff
Nroff
nroff is a Unix text-formatting program; it produces output suitable for simple fixed-width printers and terminal windows...
emulating formatter was ported to OS-9 by MicroWay, as well.
In mid 1980s, OS-9 was selected for the CD-i
CD-i
CD-i, or Compact Disc Interactive, is the name of an interactive multimedia CD player developed and marketed by Royal Philips Electronics N.V. CD-i also refers to the multimedia Compact Disc standard used by the CD-i console, also known as Green Book, which was developed by Philips and Sony...
operating system. Around the same time, Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
approached Microware for acquisition of the company primarily because it was attracted by CD-RTOS, the CD-i operating system. The negotiation failed and no deal was made; Microware decided to remain independent.
In late 1980s, Microware released OS-9000, a more portable version of the operating system. The vast majority of the operating system kernel was rewritten in C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
leaving a handful of hardware-dependent parts in assembly language. A few "more advanced features" were added such as tree-like kernel module name space. OS-9000 was initially ported to the Motorola 680x0 family CPUs, Intel 80386
Intel 80386
The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...
, and PowerPC
PowerPC
PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
. The OS-9000/680x0 was a marketing failure and withdrawn very quickly, probably because few customers wanted to try the fatter and slower operating system over the existing OS-9/680x0 proven record of stability. That the Motorola 680x0 family and VME
VMEbus
VMEbus is a computer bus standard, originally developed for the Motorola 68000 line of CPUs, but later widely used for many applications and standardized by the IEC as ANSI/IEEE 1014-1987. It is physically based on Eurocard sizes, mechanicals and connectors , but uses its own signalling system,...
board computer system vendors were nearing their end of life might have affected the unpopularity of OS-9000/680x0. Microware later started calling all of its operating systems — including what had been originally called OS-9000 — simply OS-9, and started shifting its business interest towards portable consumer device markets such as cellphones, car navigation, and multimedia.
In late 1980s and early 1990s, the Character Generators computers used in Broadcast Systems used OS-9 and OS-9000 extensively. The now defunct Pesa Electronica used OS-9 on their CGs such as CG 4722 and CG4733.
Name conflicts and court decisions
In 1999, nineteen years after the first release of OS-9, Apple ComputerApple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
released Mac OS 9
Mac OS 9
Mac OS 9 is the final major release of Apple's Mac OS before the launch of Mac OS X. Introduced on October 23, 1999, Apple positioned it as "The Best Internet Operating System Ever," highlighting Sherlock 2's Internet search capabilities, integration with Apple's free online services known as...
. Microware sued Apple that year for trademark infringement, although a judge ruled that there would be little chance for confusion between the two. Some Macintosh users who are unaware of Microware's relatively unknown OS-9 have posted to the news://comp.os.os9 newsgroup; not realising what OS-9 is.
In 2000, RadiSys purchased Microware to acquire the Intel IXP-1200 network processor resources. This acquisition infused Microware with capital and allowed Microware to continue OS-9 development and support. As of 2011, OS-9 is still supported by RadiSys and Microware.
Modern and archaic design
OS-9 (especially the 68K version and thereafter) clearly distinguishes itself from the prior generation of embedded operating systems in many aspects.- Runs on 8-bit, 16-bit, and 32-bit CPUs.
- Clear separation between user mode and supervisor (kernel) mode.
- Dynamic use of individually and separately built software components (executable program images and kernel modules) rather than a statically linkedStatic libraryIn computer science, a static library or statically-linked library is a set of routines, external functions and variables which are resolved in a caller at compile-time and copied into a target application by a compiler, linker, or binder, producing an object file and a stand-alone executable...
single monolithic image. - Unix-like process name-space model (not memory modelMemory model (computing)In computing, a memory model describes the interactions of threads through memory and specifies the assumptions the compiler is allowed to make when generating code for segmented memory or paged memory platforms.-History and significance:...
) and user shell program. - Clear separation between hardware independent (e.g. file managers) and hardware dependent (e.g. device driverDevice driverIn computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
s) layers.
When compared with more modern operating systems.
- Kernel is entirely written in assembly languageAssembly languageAn assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
(OS-9/68K version only) as well as CC (programming language)C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
(portable version to other architectures) - using simple internal data structures, reducing flexibility and improvement scope while improving determinability required for Real-time operating systemReal-time operating systemA real-time operating system is an operating system intended to serve real-time application requests.A key characteristic of a RTOS is the level of its consistency concerning the amount of time it takes to accept and complete an application's task; the variability is jitter...
s. - Performance was also affected for some operations, but assembly language helped with the speed issue.
- Systems without MMUMemory management unitA memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to memory requested by the CPU...
have no memory protection against illegal access, nor per process memory protection while systems with MMU can have memory protection enabled. The module controlling the MMU can be included or omitted by the system integrator to enable or disable memory protection. This allows OS-9 to run on older systems which do not include an MMU. - Older versions of OS-9 do not support POSIX threadsPOSIX ThreadsPOSIX Threads, usually referred to as Pthreads, is a POSIX standard for threads. The standard, POSIX.1c, Threads extensions , defines an API for creating and manipulating threads....
while all OS-9 supported processors support POSIX threads. - No SMPSymmetric multiprocessingIn computing, symmetric multiprocessing involves a multiprocessor computer hardware architecture where two or more identical processors are connected to a single shared main memory and are controlled by a single OS instance. Most common multiprocessor systems today use an SMP architecture...
support for multiple sockets, cores, or hardware threads in the same OS-9 instance (can run as a RTOS on one of the cores of dual core processors like Core Duo and Core 2 Duo, when LinuxLinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
is running on the other core doing general purpose tasks)
Task scheduling
OS-9’s real-time kernel allows multiple independent applications to execute simultaneously through task switching and inter-process communication facilities. All OS-9 programs run as processes containing at least one lightweight process (thread) but may contain an effectively unlimited number of threads. Within a process, these lightweight processes share memory, I/O paths, and other resources in accordance with the POSIX threads specification and API. OS-9 schedules the threads using a fixed-priority preemptive scheduling algorithm with round-robin scheduling within each priority. Time slicing is supported. The priority levels can be divided into a range that supports aging and a higher-priority range that uses strict priority scheduling. Each process can access any system resource by issuing the appropriate OS-9 service request. At every scheduling point, OS-9 compares the priority of the thread at the head of the active queue to the priority of the current thread. It context switches to the thread on the active queue if its priority is higher than the current processes’ priority. Aging artificially increases the effective priority of threads in the active queue as time passes. At defined intervals, time slicing returns the current thread to the active queue behind other threads at the same priority.Comparisons with Unix
OS-9's notion of processes and I/O paths is quite similar to that of Unix in nearly all respects, but there are some significant differences. Firstly, the file systemFile system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
is not a single tree, but instead is a forest with each tree corresponding to a device. Second, OS-9 does not have a Unix-style fork
Fork (operating system)
In computing, when a process forks, it creates a copy of itself. More generally, a fork in a multithreading environment means that a thread of execution is duplicated, creating a child thread from the parent thread....
system call—instead it has a system call which creates a process running a specified program, performing much the same function as a fork-exec
Fork-exec
Fork-exec is a commonly used technique in Unix whereby an executing process spawns a new program. fork is the name of the system call that the parent process uses to "divide" itself . After calling fork, the created child process is an exact copy of the parent except for the return value...
or a spawn
Spawn (computing)
Spawn in computing refers to a function that loads and executes a new child process.The current process may or may not continue to execute asynchronously...
. Additionally, OS-9 processes keep track of two "current directories" rather than just one; the "current execution directory" is where it will by default look first to load programs to run (which is of course similar to the use of PATH environment variable
Environment variable
Environment variables are a set of dynamic named values that can affect the way running processes will behave on a computer.They can be said in some sense to create the operating environment in which a process runs...
under UNIX). The other is the current data directory. OS-9 has had a modular design from the beginning, influenced by notions of the designers of the 6809
Motorola 6809
The Motorola 6809 is an 8-bit microprocessor CPU from Motorola, designed by Terry Ritter and Joel Boney and introduced 1978...
and how they expected software would be distributed in the future (see the three-part series of articles in Jan-Mar 1979 Byte by Terry Ritter, et al. of Motorola who designed the CPU).
- The module structure requires more explanation:
- OS-9 keeps a "module directory", a memory-resident list of all modules that are in memory either by having been loaded, or by having been found in ROM during an initial scan at boot time.
- When one types a command to the OS-9 shell, it will look first in the current module directory for a module of the specified name and will use it (and increase its link count) if found, or it will look on disk for an appropriately named file if not.
- In OS-9/6809 and OS-9/68000, the module directory is flat, but OS-9000 made the module directory tree-structured. The OS-9000 shell looks in one's alternate module directory for a MODPATH environment variable, analogous to the PATH variable in all versions, indicating the sequence of module directories in which to look for pre-loaded modules.
- Modules are not only used to hold programs, but can also be created on the fly to hold data, and are the way in which OS-9 supports shared memory.
OS-9/non-68000 supports POSIX threads. A single process can start any number of threads.
This rivalry went far enough that the OS-9 version 2.4 manual had this entry describing UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
in the Glossary of Appendix C of "Using Professional OS-9":
UNIX:
An operating system similar to OS-9, but with less functionality and
special features designed to soak up excess memory, disk space and CPU
time on large, expensive computers.
This entry was removed in the version 3.0 manual.
The OS-9 shell had an easter egg in its command history
Command History
Command history is a feature in many operating system shells, computer algebra programs, and other software that allows the user to recall, edit and rerun previous commands....
function, invoked by CTRL-A. Upon a fresh boot, the command history was supposedly empty, but if the user typed a single space followed by a backspace, then hit CTRL-A, the names of the authors would be displayed: 'by K. Kaplan, L. Crane, R. Doggett'.
21st century uses
- Versions of OS-9/68K run on a wide variety of 68000 family platforms, including the Sharp X68000Sharp X68000The Sharp X68000, often referred to as the X68k, is a home computer released only in Japan by the Sharp Corporation. The first model was released in 1987, with a 10 MHz Motorola 68000 CPU, 1 MB of RAM and no hard drive; the last model was released in 1993 with a 25 MHz Motorola 68030...
in Japan, some personal computers intended by their designers as upgrades from the Color Computer (e.g., the 68070 and 68340-based MM/1, and on other computers from Frank Hogg Laboratories, PEPPEPPEP may refer to:In computing:*Packetized Ensemble Protocol, used by Telebit modems*PEP tool, a programming environment based on Petri nets...
, and Delmar Co.) It was also ported to the Atari STAtari STThe Atari ST is a home/personal computer that was released by Atari Corporation in 1985 and commercially available from that summer into the early 1990s. The "ST" officially stands for "Sixteen/Thirty-two", which referred to the Motorola 68000's 16-bit external bus and 32-bit internals...
by Recc-o-ware in the early 1990s, and was distributed by Cumana in Europe. A port to the AmigaAmigaThe Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
is also purported to exist. - OS-9/68K is also found in some embedded applications, including the Quanta Delta television broadcast character generator, still in production by ScanLine Technologies in Utah. While the user-level interface code on this system started at boot time, there was a hidden, undocumented keyboard sequence that would provide a user with a root shell prompt in a scroll window on the device's edit-channel monitor.
- In the embedded market, where OS-9 has found application in such devices as the FairlightFairlightFairlight is a digital audio company based in Sydney, Australia. In 1979 they created the Fairlight CMI, the first digital audio sampler, quickly used by artists such as Peter Gabriel, Kate Bush, and Jean Michel Jarre. They are now a manufacturer of media solutions tools such as digital audio...
CMI synthesizers, robotics, in-car navigation systems, and PhilipsPhilipsKoninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
' Compact Disc-Interactive (CD-iCD-iCD-i, or Compact Disc Interactive, is the name of an interactive multimedia CD player developed and marketed by Royal Philips Electronics N.V. CD-i also refers to the multimedia Compact Disc standard used by the CD-i console, also known as Green Book, which was developed by Philips and Sony...
) industry standard. - The TRS-80 Color ComputerTRS-80 Color ComputerThe Radio Shack TRS-80 Color Computer was a home computer launched in 1980. It was one of the earliest of the first generation of computers marketed for home use in English-speaking markets...
(and clones) still has users and an annual conference in Chicago; as of 2007 the 17th Annual "Last" Chicago CoCoFEST is scheduled for April 2008. A group of Canadian programmers rewrote OS-9/6809 Level II for the CoCo 3 (w/ address translation hardware) for efficiency, and to take advantage of the native modeNative modeThe term native mode or native code is used in computing in two related senses.*to describe something running on a computer natively or in native mode meaning that it is running without any external support as contrasted to running in emulation....
of the Hitachi 6309Hitachi 6309The 6309 is Hitachi's CMOS version of the Motorola 6809 microprocessor. While in "Emulation Mode" it is fully compatible with the 6809. To the 6809 specifications it adds higher clock rates, enhanced features, new instructions, and additional registers...
. Today's serious CoCo users now typically have replaced the 68B09E in the CoCo 3 with an Hitachi 63B09E and run the rewrite, called NitrOS9. The combination is surprisingly fast, considering that it runs on an expressly low cost, 8-bit computer system. - OS-9000/80x86 can be run on PC-type machines built around the Intel x86 CPUs. OS-9000 has also been ported to the PowerPCPowerPCPowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
, MIPSMIPS architectureMIPS is a reduced instruction set computer instruction set architecture developed by MIPS Technologies . The early MIPS architectures were 32-bit, and later versions were 64-bit...
, some versions of Advanced RISC Machines' ARMARM architectureARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...
processor, and some of the Hitachi SH familySuperHSuperH is a 32-bit reduced instruction set computer instruction set architecture developed by Hitachi. It is implemented by microcontrollers and microprocessors for embedded systems....
of processors. - The DigiCart/II Plus audio playback unit runs OS-9/68K. It is a solid state replacement for radio station style cart8-track cartridgeStereo 8, commonly known as the eight-track cartridge, eight-track tape, or simply eight-track, is a magnetic tape sound recording technology. It was popular in the United States from the mid-1960s through the late 1970s, but was relatively unknown in many European countries...
players. These units are used in radio and at places like Walt Disney World where they play park announcements. - German electronics manufacturer Eltec has been manufacturing the Eurocom-model CPU boards for industrial purposes since the late seventies, starting with the 6802 and 6809 Eurocom-1 and Eurocom-2, and onwards with 68K, and derivative, CPU boards up to today. The modern boards can be delivered with a range of operating systems, amongst which is OS-9.
External links
- Microware and Microware OS-9, from the RadiSys website
- Archive of OS-9 information and software, including an OS-9 FAQ, from Real-time Services Inc.
- Repository for command line tools for manipulating 6809 OS-9 disk images, on SourceForgeSourceForgeSourceForge Enterprise Edition is a collaborative revision control and software development management system. It provides a front-end to a range of software development lifecycle services and integrates with a number of free software / open source software applications .While originally itself...
- Execution environment for OS-9 user-mode programs on Mac/Win/linux host OS
- NitrOS-9 official website, on SourceForgeSourceForgeSourceForge Enterprise Edition is a collaborative revision control and software development management system. It provides a front-end to a range of software development lifecycle services and integrates with a number of free software / open source software applications .While originally itself...
- An OS-9 Port to the Thomson MO5
- comp.os.os9 newsgroup via Google groups web interface.
- Official OS-9 Blog
- A 6809 Emulator based on the SWTPC 6809 system that runs OS9 and UniFLEX as well as FLEX
- Access OS-9 disk on PC
- XiBase9 (a GUI)
- DragonWiki