[x264-devel] Off topic: how to discover SSE2 units

[Holger Lubitz]

On Wed, 2010-12-01 at 11:39 +0100, Eeri Kask wrote:
> In particular, how may SSE2 units does intel quad-core xeon in a
> MacPro of early 2008 have?  I kind of remember hearsay telling some
> intel multi-core CPUs have one SSE2 unit which is then shared among
> all cores; which would mean parallel-running multi-threaded programs
> utilising SSE2-instructions are serialised at that point... not so?  :-)

Obviously not. What would be the point of having separate cores if they
still had to share execution resources? That's what happens in
hyperthreading, where two threads run on the same core. Of course each
core has its own SSE "unit". Or to be exact, there is no specific SSE
unit. Each of the normal execution units p0/p1/p5 handles some SSE
commands too, so your SSE commands compete with other instructions in
the queue of the same thread (or the other HT thread on this core) for
execution resources, but not with threads on other cores.

Holger