[OT] End-user uses for x86-64 (was: Why are still not at 64 bits)

[Jon 'maddog' Hall]

> Does throughput double without re-writing all the code to take
> advantage of that?
Yes.

And other issues such as double-word arithmetic (especially in floating
point) are done as a single clock-tick.  But this has little to do with
larger address space.

> 
>   The second is semi-historical: As I recall, your argument is the
> same argument Intel put forth in favor of Itanic -- I mean, Idiotanium
> -- I mean, Itanium -- and we all know that is going nowhere at
> velocities approaching C.
> 

/*HOLD FOR BIGGEST RANT OF MONTH*/

The Itanic did not take off because it simply broke all binary
compatibility on the theory that they could make it up with emulation
and everyone would be happy.  Wrong on both counts.

The Itanic's instruction set was (and I use the past tense purposely) an
ultra-wide instruction set that was studied and rejected in computer
science years ago, but it still keeps coming up like bad coffee, and
some jerk in Intel/HP probably thought that they could get a couple of
patents on the instruction set to keep AMD from copying it.

Complex instructions sets in general, and ultra-wide instruction sets in
particular, are a compiler-writer's nightmare.  They are "tuned" to
particular job flows that we have no idea what they are, where they come
from, or if they ever will exist.

Compare this to the Alpha, with its very clean RISC instruction set that
allows the language choice, compiler choice, and pragmas to tell the CPU
what the job flow will be and how to optimize.  And THEN, even after
creating the object code, the CPU would re-optimize instruction and
register execution on the fly.

I know that Intel did not invent complex instructions, but they have
done more to break compiler-writer's hearts than any other company.

Thank heaven AMD made them understand that compatibility was important,
and that you did not have to throw the baby out with the bathwater.

/* END OF RANT*/

And if I never see another ultra-wide instruction again, my life will be
much happier.

maddog