Re: Pentium SSE prefetcht0 instruction... How do you make it work

Robert Love (
27 Sep 2001 15:55:35 -0400

On Thu, 2001-09-27 at 14:43, Tony Hagale wrote:
> Intel's p3/4 prefetch instructions are hints only. They are only executed
> asynchronously, and depend heavily on the other load on the processor at
> the time. They are not required to prefetch, *and* they are not required
> to be executed when you think they should in the flow of the program. You
> can serialize them by using an MFENCE instruction, but they still aren't
> guaranteed to run.
> Check the p4 manuals. In fact, I'm not sure prefetch was implemented in
> p3. I could be wrong, check the manual.

prefetch is in P3 and P4.

there are prefetcht0, prefetcht1, prefetcht2, and prefetchnta
instructions, Intel's programming docs have references on these all

Robert M. Love
rml at
rml at

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