> 	This is both right and wrong: some optimizations are processor
> specific and those are not used in distributed binaries.

It is possible to make a further distinction among processor-specific
optimizations:

- some use features that are specific to a certain processor, or available
  only above a given release, and will result in binaries that do not work
  on other processors;

- some use only generic features, but tune the code according to the
  strengths and weaknesses of a given processor, and will result in binaries
  that run on others processors, only slower than a binary with generic
  optimizations.

For example, optimizing for Pentium 4 may mean using SSE2, causing
incompatibility with earlier processors, but it may also mean tuning for the
long pipeline, causing just slowness.

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