prefetching on pentium4

[ranjith kumar]

Hi,
    There are 4 types of prefetch instructions on
pentium 4 (IA-32) processor.
prefetchnta,prefetcht0,prefetcht1,prefetcht2.

In case of pentium 4, IA-32 otimization manuvals say
that prefetcht0,prefetcht1,prefetcht2 are identical.

It also says ONLY prefetchnta instruction prefetches
data into L2 cache without poluting caches.

 When all the four instructions prefetches data into
L2 cache (not into L1 cache) , what is the meaning in
saying prefetchnta does not polute caches?

ie)what is the difference between prefetchnta and
other instructions?


Thanks in advance.



 
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