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From: johns@rd.scitec.com.au (John Saunders)
Subject: Re: Real-time systems:  Windows-NT or QNX
Message-ID: <1994Oct19.015007.12567@rd.scitec.com.au>
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References: <FriOct14102309EST1994@eric> <PLM.94Oct17160537@nijmegen3.atcmp.nl>
Date: Wed, 19 Oct 1994 01:50:07 GMT
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Xref: glinda.oz.cs.cmu.edu comp.realtime:7236 comp.os.qnx:2282 comp.os.ms-windows.advocacy:40855 comp.robotics:14540

Peter Mutsaers (plm@atcmp.nl) wrote:

> 2000Hz loop you mention a bit later. That is very fast. I doubt if a
> 486 can handle that, and if it can, then without doing anything else.
> I have made a robot controller running at 300Hz, and we used a 68040
> for that (on a VME bus) dedicated for this 300Hz loop (interrupt level
> code).

> If you need 1000Hz or more, you should use special purpose hardware
> such as some DSP board for the inner loop.

Just to put things in perspective, handling a 9600 baud serial link
generates almost 1000Hz interrupts. Handling 19200 baud will generate
almost 2000Hz interrupts.

It's not so much the interrupt rate but what you do inside the
interrupt handler. If you expect to do more processing than a serial
driver then it's time to find another solution or more powerful
hardware.

The last job I worked on had an 80188 @ 16MHz handling 3 9600 baud
serial lines (~3K interrupts per second). The user interface processing
would noticably slow down when all 3 links were being used (but no
serial characters were lost). All drivers were hand optimised
assembler which helps.
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