On Sun, Jul 02, 2000 at 04:30:19PM +0200, Andrew Tuckey wrote:
> Hi RTLinux list,
>
> I'm new to real-time Linux, so this question may seem a little simple.
>
> I'm implementing a machine controller on a dedicated system and I'd like to
> see if I could do it on a more general system with RTLinux. The system has a
> sample rate of 10kHz and is currently implemented on a couple of TMS320C40s.
>
> I have read a fair amount of the literature on RTLinux available on the web
> site and it seems to me that the major problem with using RTLinux would be its
> interrupt latency. From the literature it seems that the worst case interrupt
> latency can be as high as 15 to 20 us - this is a large amount of the
> available 100 us and would be a major problem.
>
> I would imagine that this interrupt latency is solely caused by the amount of
> time required to switch contexts - i.e. push all the registers etc.
Good guess, but that's not right. The major factor is purely motherboard
hardware. We have not measured recently on a good non-ISA SBC, but my
prediction is that it would be quite fast.
In fact, we really will measure on a embedded PPC750 and MIPS 7000
soon and perhaps other people can also run some numbers.
(we have measured 12us for a single ISA bus access !)
--
---------------------------------------------------------
Victor Yodaiken
FSMLabs: www.fsmlabs.com www.rtlinux.com
FSMLabs is a servicemark and a service of
VJY Associates L.L.C, New Mexico.
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