Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!dali.cs.montana.edu!masscomp!swoyer
From: swoyer@masscomp.ccur.com (Ted Swoyer)
Newsgroups: comp.realtime
Subject: Re: Real-Time Operating Systems
Message-ID: <31669@masscomp.ccur.com>
Date: 20 Jul 90 00:10:59 GMT
References: <2931@zipeecs.umich.edu>
Reply-To: swoyer@westford.ccur.com (Ted Swoyer)
Organization: Concurrent Computer Corp. - Westford, Ma
Lines: 99

In article <2931@zipeecs.umich.edu> walden@dip.eecs.umich.edu (Eugene Marvin Walden) writes:
>
>   I was wondering if anybody knows of any other commercial real-time operating
>systems than the ones listed below:
>
>   1. VRTX (Ready Systems)
>   2. IRMX (Intel)
>   3. QNX (Quantum Software)
>   4. VxWorks (Wind River Systems)
>   5. OS/9, OS/9000 (Microware)
>   6. Alpha (Concurrent Computer Corp.)
>   7. Kadak
>
>   All of the above except #6 (Alpha) are really not true real-time operating
>systems, because there is no provision for handling deadlines. The Alpha op-
>erating system is state-of-the-art, but I don't know anything about its avail-
>ability. 
>   So here's the question-- anybody have any other RTOSs that they know of? I
>am particularly interested in a system that has something more sophisticated 
>than a simple priority-based scheduler, but any other additions would be use-
>ful as well.
>

You missed Concurrent Computer Corp.'s RTU operating system. RTU is a
System V Release 3 compliant operating system with extensive enhancements
to support real time applications. RTU also provides a 4.2BSD compatibilty
environment for easy porting of Berkeley based applications.

RTU is available on Concurrent's line of multiprocessors including a
Motorola 68020 platform, a Motorola 68030 platform and a MIPS R3000
platform.

RTU's enhancements are in the following domains:

Multiprocessing
	RTU supports symmetric multiprocessing, threads and compilers
	enhanced to provide parallelization. RTU also supports directed
	interrupt handling to free up all but the boot processor from
	handling interrupts (normally interrupts are symmetricly handled),
	distribution of interrupts so specific CPUs can process specific
	interrupts or interrupt levels, automatic process scheduling
	among time-sharing processors from a single run queue, user control
	over the processors on which processes may run (at run time or
	shell command execution) (all, several or one - with a choice
	of which one(s)) and a real-time slave environment which
	essentially dedicates the slave processor(s) to an interrupt
	source in bare metal (but with system services standing by).
Preemption
	RTU supports process preemption in both kernel and user space,
	allowing higher priority tasks to run as soon as they are ready
	even if a lower priority process is executing a system call.
Scheduling
	In addition to the standard UNIX scheduling policy, RTU supports
	a fixed priority policy and a fixed priority with quantum
	policy (round robin with fixed priority). The next version of
	RTU will include a synthetic period scheduler (capable of
	synthesizing an execution pattern synchronous to a given
	frequency).
Memory management
	RTU supports locking a either all or part of a process into memory.
	Either text, data or both can be locked in using the System V
	block(2) system call or individual pages of text, data or
	stack can be locked using an RTU system call. A process with
	locked pages will not swap.
Interprocess communication and synchronization
	RTU supports an Asynchronous System Trap mechanism for kernel
	to user or user to user communication. ASTs can be assigned
	different priorities, can pass information from the sending
	to receiving process, are queued, are serviced by priority
	order (32K priorities) and will never be lost. RTU also
	supports the System V shared memroy, semaphores, message queues,
	named pipes, memory based pipes, STREAMS and signals and BSD sockets
	and signals. In addition, RTU supports reserved memory to allow
	direct, unmediated communication between user address space and
	devices on the system bus. Reserved memory can also serve as a
	contiguous shared memory area.
I/O
	In addition to the standard UNIX I/O mechanisms, RTU supports
	asynchronous I/O, I/O bus addressing, direct DMA to and from
	user space, synchronized I/O, multiple I/O buses, contiguous
	disk files, bit mapped disk allocation, preallocated files,
	direct I/O which bypasses the UNIX block buffering, exclusive
	disk operation and support for symmetric device driver. In the next
	release RTU will support disk mirroring, disk striping and disk
	dual porting.
Deterministic response
	RTU essentially allows successive redirection of processing
	until what is left is just the process tied to just the interrupt
	or interrupt level running on 1-7 processors with direct
	access to the disk subsystem. This environment is called the
	real-time slave environment. All system services are also availabe
	in this environment, but process dispatch latencies will differ
	depending on the system services in use.

If you want further information about RTU or Concurrent, contact me at
(508) 392-2690.

Ted Swoyer