DOCUMENT:Q94265  20-JUL-1993  [W_NT]
TITLE   :Windows NT and Real-Time Operating Systems
PRODUCT :Windows NT
PROD/VER:3.10
OPER/SYS:WINDOWS
KEYWORDS:

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The information in this article applies to:

 - Microsoft Windows NT operating system version 3.1
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Summary:

You can use a variety of criteria to measure the performance of a
real-time system. The following are examples of the kinds of
measurements that might be used to determine real-time throughput:

 - Longest critical region that the kernel blocks task activation
   during a system call

 - Maximum time that interrupts are disabled

 - Context switch time (scheduler time to save/restore registers,
   etc.) for threads within the same process (no change in memory
   context) and for threads in different processes (save/restore
   memory context)

 - Interrupt response time (latency between the occurrence and execution
   of the first instruction)

 - Interrupt task response time (worst case task dispatch latency for
   task waiting on the interrupt)

 - Performance of interprocess communication facilities (semaphores,
   queues, pipes, etc.)

Because such specifics are hard to measure, this article provides a
general discussion of the suitability of Windows NT as a real-time
system.

More Information:

Users often want a total program development/GUI user environment,
virtual memory, and so forth, without any corresponding reduction in
response time. Real-time systems, however, are dedicated systems for
the duration of an "event." During that time, the system is
essentially locked, and no other activity can take place except that
real-time event. (Note that very few situations demand microsecond or
millisecond response time.) 

Windows NT has the same basic structure as VMS. Windows NT has more
efficient mechanisms than RSX-11M. It has a better design than VAXELN, 
which is a real-time embedded OS toolkit. All three of these systems
are very successful.

Although Windows NT has good real-time capabilities; it is not
designed to compete with  a special purpose real-time system. If you
need such a design, you should obtain a suitable operating system. 

Additional reference words: real time realtime winnt


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