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Re: interrupt latency (ARM7)


On Wed, 2001-10-17 at 06:41, Jonathan Larmour wrote:
> Ilko Iliev wrote:
> > 
> > I have custom board with ARM7 (AT91M55800) at 33Mhz system CPU clock.
> > 
> > I measured ISR handling latency time 48-90 mkSec.
> > 
> > It is normal???
> 
> Maybe; it depends on a whole lot of things like speed of RAM, speed of ROM
> (if you're running from ROM) and the settings of quite a few options in the
> eCos configuration. I can guarantee it could be reduced by using different
> configuration options; the default configuration is not the fastest!

Other things can affect this greatly.
  * Does this system run from ROM/FLASH or RAM?
  * Does the CPU have caches?  what size?  are they enabled?

Many of the "simpler" ARM7 device cores do not have any caches which 
serverly impacts their performance.

Just a few things to think about.


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