ia32e, er EM64T that is...

Jakub Jelinek jakub at redhat.com
Tue Sep 7 06:37:02 UTC 2004


On Mon, Sep 06, 2004 at 10:44:47PM -0700, Bryan O'Sullivan wrote:
> On Mon, 2004-09-06 at 13:47 -0400, Alan Cox wrote:
> 
> > em64t as Intel currently call it is pretty close to the x86-64 architecture
> > so its not too bad a clone. It lacks prefetch/prefetchw which can also be 
> > used by some fancy user space stuff like image processors. 
> 
> Er, EM64T provides the SSE prefetch{nta,t[012]} instructions, which are
> somewhat more expressive than prefetch anyway, and which also run on AMD

Somewhat more and somewhat less expressive to be exact.
SSE prefetches allow you to specify locality very well, 3dNOW prefetch
allows prefetching for write, but no locality.
If GCC knows both SSE and 3dNOW prefetches are available, it will use
3dNOW prefetch for __builtin_prefetch (p, 1, [0-3]) (and disregard
the locality) and SSE prefetch for __builtin_prefetch (p, 0, [0-3])
(where locality is used).

> chips.  Shame about the lack of a prefetchw analogue, but it's hardly a
> surprise that Intel isn't implementing 3dnow.

	Jakub





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