Newsgroups: comp.realtime,comp.os.qnx,comp.os.ms-windows.advocacy,comp.robotics
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From: altstadt@radon.mpr.ca (John Altstadt)
Subject: Re: Real-time systems: Windows-NT or QNX
Message-ID: <1994Oct18.154244.8760@mprgate.mpr.ca>
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References: <FriOct14102309EST1994@eric> <37kql1$e4d@vixen.cso.uiuc.edu> <FAT.94Oct18122551@Indy>
Date: Tue, 18 Oct 1994 15:42:44 GMT
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Xref: glinda.oz.cs.cmu.edu comp.realtime:7219 comp.os.qnx:2267 comp.os.ms-windows.advocacy:40772 comp.robotics:14500

In article <FAT.94Oct18122551@Indy>, fat@Indy (Irtegov Dmitry Valentinovich) writes:
>May be I'm lost original topic :(. I know that OS/2 is NOT a real-time OS.
>It is not a FUD, not a M$ Windose advocacy. It is a solid fact.
>
>If you ain't know, real-time system is system that is designed to work
>in hard answer-time conditions, i.e. external event MUST be processed in
>a given amount of time, often in several microsecs. Multitasking VM OS
>is required to have special features to be real-time, such as: special 
>Real-Time sheduling class (higher priority than system processes), ability 
>to lock parts of address space into RAM, special design of the kernel 
>(nowadays it is called mikrokernel. BTW RT-11 has had in in early 70s) 
>and good interprocess communication facilities. Note: being 
>mikrokernel-based does not mean being Real-Time.
>
>It is a solid fact that OS/2 *DOES NOT HAVE* these features (exept IPC).

From page 135 of "The Design of OS/2", H. M. Deitel, M. S. Kogan:

"OS/2 guarantees that a time-critical thread that is made ready to run
will be dispatched within 4 milliseconds."

Not great (no explicit lower bound), and not overly fast, but it does
exist.  Unfortunately, they don't state any mechanisms used, so it is
unclear whether it will be any faster for a 100 MHz pentium than it is
for the original 286 that OS/2 1.0 was designed for.

Note that the space shuttle is rumored to use a 25 Hz process schedule.

OS/2 can easily be configured by the user to lock everything into RAM by
changing a single line in CONFIG.SYS.  And for the programmers in the
crowd, from page 256 in Deitel & Kogan:

"Functions are provided for locking memory, managing scatter-gather page
lists, and performing address translation."

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