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VxWorks, from Wind River Systems, is a networked real-time operating system designed to be used in a distributed environment. It runs on a wide variety of hardware. It requires a host workstation for program development; supported host platforms include Sun3, Sun4….
Is the run-time component of the Tornado 3 embedded development platform.
The VxWorks RTOS comprises the core capabilities of the wind microkernel (not monolithic) along with advanced networking support, powerful file system and I/O management, and C++ and other standard run-time support.
The development environment is based on cross-development or remote-development method. You will need a UNIX machine of some sort (e.g. SUN's) to run the compilers and debuggers. The compiled application code can be downloaded to the target and runs as part of the VxWorks image. During the development phase or thereafter, individual object code (.o files) can be downloaded dynamically to running target system. Finished applications can be ROM'ed or whatever.
VxWorks most definitely is not a "realtime UNIX", or a varient of UNIX as often misunderstood by some people. The confusion perhaps is due to the fact that UNIX hosts are used most widely to develop applications for VxWorks (and VxWorks itself).
WRS was started by Jerry Fiddler and David Wilner in Jerry's garage as a contract/consultant shop for realtime, embedded systems and other fun things. They wrote a bunch of neat programs for their work and eventually adding some things unheard of in embedded/realtime market in those days such TCP/IP networking. And continued to pioneer in this area by adding NFS, etc.
VxWorks was the name given the collection of software which ran on top of various realtime kernels including VRTX and pSOS as well an earlier slower version of WIND kernel. VxWorks now no longer runs on other kernels; it now runs exclusively on its own WIND kernel since the 5.0 release, for which the WIND was rewritten by John Fogelin.
VxWorks runs in one mode. No protected vs. user mode switching is done. Running in supervisor mode on most processors, and not using traps for system calls, VxWorks can achieve minimal overhead on a given piece of hardware than UNIX. Programming on VxWorks can be more tricky than UNIX for the same reason.
UNIX provides resource reclamation; by default, VxWorks does not.
VxWorks does not have full "process"; it only has tasks, or "threads".
VxWorks: minimal interrupt latency (e.g. spl's are quasi-implemented as semaphores). Traditional UNIX: high interrupt latency (e.g. spl's are implemented as interrupt lock and unlock calls).
VxWorks: priority interrupt-driven preemption, optional round-robin time-slicing. Traditional UNIX: prioritized round-robin preemptive time-slicing. Since VxWorks is just a glorified "program" it can be changed and customized pretty easily. Task scheduling can be customized as desired.
VxWorks networking code, however, is very UNIX compatible. It is essentially "ported" version of BSD UNIX TCP/IP code -- tahoe release .