Re: [ECOS] Performance problem mpc8xx

[Jesper Skov <jskov at redhat dot com>]

On Fri, 2002-05-17 at 09:50, Daniel.Andersson@combitechsystems.com
wrote:
> Hi,
> 
> I am having some performance problem on my MPC850 board. When i setup a very
> small main that only executes like 100 asm instruction then it takes around
> 6-7 times the teoretically time. My first thought was that the caches wasnt
> turned on but when i turned them off - before my short loop - as a test,
> then i got a further decrease of performance (3.5 times).
> 
> Does anybody have any ideas of what maight be wrong here?

Could be serialization which has not been switched off. It prevents the
CPU for executing more than one instruction at the time. I'm pretty sure
we switch that off in the 8xx HAL though.

Something else: we had an internal bug on bad dhrystone performance on
the 850. It's closed now, and turned out to be due to the caches not
being set up correctly. I don't know exactly what the fix was. But you
can look for it in eCos V2...

Jesper



Jesper


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