Subj : Re: AMD has cmpxchg16b now - sort of
To   : comp.programming.threads
From : nathanw
Date : Tue Mar 08 2005 05:52 pm

"Joe Seigh" <jseigh_01@xemaps.com> writes:

> No I meant versioning.  When they add a new architectural feature,
> it becomes present on every processor of a certain version or later.
> That way, all you need to know when getting a processor is the version
> number.

That means that having added feature X and then feature Y, they can't
sell something with Y but without X. Given the number of niche
markets, specialized applications, and so on, no vendor is going to
restrict themselves that way.

> > Option bits are a pretty well entrenched mechanism for this on several
> > architectures (not, notably, PowerPC, where you have to have a lookup
> > table based on the CPU ID to find out if you have an FPU, AltiVec, or
> > whatnot).
> >
> The synchronization stuff for powerpc was pretty well in place from the
> very beginning.

Synchronization, sure, but there are lots of other features one is
interested in testing and that have varied across PowerPC
implementations (FPU, SIMD/vector instructions (including, but not
limited to AltiVec), string instructions, handling unaligned data
automatically, and so on).

        - Nathan

.