Newsgroups: comp.realtime,comp.os.qnx,comp.os.ms-windows.advocacy,comp.robotics
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From: rgallen@muug.mb.ca (Rennie Allen)
Subject: Re: Real-time systems: Windows-NT or QNX
Message-ID: <1994Oct14.152700.5798@muug.mb.ca>
Organization: Manitoba Unix User Group, Winnipeg, Manitoba, Canada
References: <FriOct14102309EST1994@eric> <37lndh$ph7@nyx.cs.du.edu> <37lvdp$iho@eccdb1.pms.ford.com>
Date: Fri, 14 Oct 1994 15:27:00 GMT
Lines: 41
Xref: glinda.oz.cs.cmu.edu comp.realtime:7123 comp.os.qnx:2190 comp.os.ms-windows.advocacy:40350 comp.robotics:14347

In <37lvdp$iho@eccdb1.pms.ford.com> wiz@rcsg30.eld.ford.com (Joseph Stanley (Joe) Wisniewski) writes:

>In article <37lndh$ph7@nyx.cs.du.edu>, njacobs@nyx.cs.du.edu (Nick Jacobs) writes:
>|> bernie@ecr.mu.OZ.AU (Bernie Kirby) writes:
>|> 
>|> >Anyway I've narrowed it down to two (or three) operating systems:
>|> >Microsoft Windows, Windows NT, and the QNX operating system from Quantum
>|> >Computer systems.  What I'm really seeking is knowledgeable advice on the
>|> >best approach, or failing that peoples opinions on how best to do what
>|> >we are trying to do.
>|> 
>|> Forget Windows for real time. QNX is a good choice for what you want
>|> to do, but how did you narrow it down to these? Did you consider
>|> pSOS, also a reasonable choice? There's also OS9000 but it
>|> hasn't the reliability of QNX ot pSOS yet, IMHO.
>|> 
>|> >connected to a clock or should they run as separate tasks?  Is it best
>|> >to have a rate generator board or can be the PC's clock be used?
>|> 
>|> The PC has a real-time clock, separate from the time-of-day clock,
>|> that runs at 1024Hz. If you need ticks faster than this you need
>|> a seaprate board.
>|> 
>If the real time clock is a deciding factor, QNX allows the motherboard
>clock to be reprogrammed. I've run mine up to 2000Hz (0.5mS) without
>problems, but the overhead of running that high speed consumes about 10%
>of a 486/66 machine. I would bet that the QNX kernal is leaner and meaner
>than NT, and that NT would perform much worse with this small a time slice.
>I tried this with Windows once, and had trouble at 200Hz (5mS).

I'm a big NT proponent.  NT with MKS Toolkit, and X Windows is the ultimate
development environment... AS LONG AS there is a QNX machine somewhere on the
net :-)

As for using NT for realtime... forget it.  It would be very funny to watch
NT running (not!) with a .5ms tick size.

email: rgallen@muug.mb.ca
QUICS: rgallen (613) 591-0934
Voice: (204) 367-2311
Fax:   (204) 367-4407
