Subj : Re: AMD has cmpxchg16b now - sort of
To   : David Hopwood
From : Joe Seigh
Date : Wed Mar 09 2005 08:15 am

On Wed, 09 Mar 2005 04:14:52 GMT, David Hopwood <david.nospam.hopwood@blueyonder.co.uk> wrote:

> Using a feature bit doesn't preclude specifying that the feature bit
> must be set on all processors above a given version. In practice that
> is the usual policy, even if it isn't written down: it's almost unheard
> of for manufacturers to remove features once they have been added to a
> given processor line.
>

Somebody on comp.arch suggested that cmpxchg16b might not stay in Intel
x86-64.  AMD probably added cmpxchg16b to stay compatible with Intel.
Things aren't chiseled in stone yet.  I think you'd have to wait until the
next generation of processors to see if they start documenting it as
being present as of a certain generation like cmpxchg8b which is documented
as being i586 or later.

Anyway, I think you just jinxed it.  As soon as someone says something
won't happen because it has never happened in the past, it will happen.  :)

-- 
Joe Seigh

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