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

[Thomas Charron]

On 2/17/07, Ben Scott <dragonhawk at gmail.com> wrote:
> On 2/17/07, Thomas Charron <twaffle at gmail.com> wrote:
> >>  People may giggle, but the PS2 Emotion processing chip is 128 bit.
>   I believe it has 128-bit floating point/vector data processing
> capabilities, but the integer registers are 64-bit, and the address
> word is 32-bit.  Right?  If so, in the context of most of the
> discussion in this thread, it would be classified as a 32-bit
> architecture.

The integer registers are 128 bit on the Emotion chip.  Address words
is a tough one, as it works in a mixed mode.  As maddog pointed out,
the memory addresses are 32 bit.  But everything INSIDE the chip is
128 bit.  To make it even more confusing, the other processors in the
system are 64 bit.  But the use of a 32 bit memory register is simply
a space saving detail.  The processors in the PS2 could very easily
handle 64 bit memory addressing, but why bother and waste the space if
you know it will NEVER need to address memory in those quantities.

>   For that matter, doesn't MMX or one of it's follow-on acronyms add
> special-purpose 128-bit registers to x86?

I'm not aware of any 128 bit registers, maybee in SSE2/3?  There where
some 64 bit registers, however.

>   I'm not trying to imply the pee cee is anything like the PS2; I'm
> just pointing out that there are a lot of things about a processor
> that get measured in "bits".  Address word size.  Instruction word
> size.  Integer registers.  Floating-point registers.  Memory bus(es).
> I/O bus(es).  Number of pieces it breaks into when you hit it with a
> hammer.  Etc.

  Exactly my point.  There are 32 bit processors that can handle 64
bit.  Most of the focus here seemed to be pretty much purely on the
ability for a 64 bit processor the address additional memory, and
that's a side effect, really.  To sum it up, a 64 bit processor can do
more advanced math sheet faster, which is in turn what makes it able
to do the mom and pop stuff faster.  Generally speaking, almost
anything can run faster, for the most part, on a 64 bit processor, but
they can't do anything that CAN'T be done (granted, with a sometimes
significant performance hit) with a 32 bit processor.

-- 
-- Thomas