[2] Help, VERY, VERY strange RTEMS execution time...

[Alex]

Hi Adrian and first thanks for your help!

Well, I am using a intel celeron mendocino at 400MHz with 128k of cache

I turned off the CPU L1 cache and CPU L2 cache using the BIOS setup...

Without turn off any cache I saw the following values:
1440
56
56
56
56
54
56
56
56
56

When I turn off the L1 and L2 caches I saw
461
54
56
56
56
54
56
56
56
56

But as you said I just turn off the data caches, right?

Ok, I have to find out how to turn off the instruction cache and then try again to see the results...

Many thanks

Alex




> 
>    Hi,
> 
> I doubt very much that you have disabled the instruction cache.
> 
>    I do not know what processor you are using, as i686 is not a 
> processor name, but as this indicates a processor at least as 
> recent as 
> the Intel Pentium Pro, all such processors have at least three 
> caches: 
> level 1 instruction cache, level 1 data cache and level 2 data cache.
> 
>    All these caches are enabled and disabled separately, so I am 
> curious what exactly have you done to disable all of them.  If you 
> just 
> used some option in the BIOS Setup of the motherboard, then most 
> BIOS'es 
> only disable the data caches, so in that case the results you have 
> measured are perfectly normal, because the instruction cache is 
> still 
> enabled.  Therefore the first result corresponds to fetching the 
> instructions from the main memory and the next values are for 
> fetching 
> from the instruction cache.
> 
> 
>    Best regards !
> 
> 
> 

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