Re: [hatari-devel] Adding cache support for the MegaSTE

[Christian Zietz <czietz@xxxxxxx>]

Nicolas Pomarède schrieb:

> from the result it means that we have cache hit when reading
> (total=$df). This is slower than 3rd test ($a7) but that's because we
> have 16384 writes instead of 8192 writes.

One problem with interpreting these numbers is that you have to consider 
that your code is also uncached or cached, depending on the machine 
config. Hence, if you do, e.g., ...

loop:
MOVE.W (A0)+,D0
DBF D1,loop

... you'll have some memory accesses for code (that are cached for sure 
when the cache is on) and just one memory access for data, which is what 
you are actually testing for.

To distinguish between these situations, I suggest that you enhance your 
program: In one test, you invalidate the cache and read memory that you 
didn't write before. This will give you the number when you have cache 
hits for code and cache misses for data. In a second test, you 
invalidate the cache, write data and read it back. This will give you 
the results with cache hits for code *and* data.

(Actually, because of the cache topology, even in the second test your 
code will replace a few words of data in the cache, causing some misses.)

Regards
Christian
--
Christian Zietz  -  CHZ-Soft  -  czietz@xxxxxxx
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