[Info-vax] HP Users Hope Whitman Can Persuade Oracle to Change Itanium Decision

[Michael S]

On Oct 2, 6:19 pm, MG <marcog... at SPAMxs4all.nl> wrote:
> On 2-10-2011 17:06, Michael S wrote:
>
> > I guess, my point is that by now Itanium has to live and die as
> > "enterprise" CPU. It is completely out of High Performance Computing
> > picture and not expected to come back.
>
> Since when is VMS in the HPC racket?
>
>   - MG

O.k. Let's go back to your original post.
You claim, absolutely correctly, that current Xeon-MP can't generate
physical address wider than 44 bits and that there is no such
limitation in current Itanium.
Since when 44 bits = 16 TB insufficient for anything but big bad
single system image HPC?
The answer is - may be it will become insufficient in 2-3 years
period, but by now it is sufficient. To prove it, let's look at
biggest IBM Power box, p795. It holds 8 TB max.
So, by now, for all enterprise class machines, not just for those
running VMS, Itaniums capability to address >50 bits (I don't remember
the exact number) of physical memory does not constitute advantage
over Xeon-MP's 44 bits.
Now, what would happen 3 years from now? Obviously, next Xeon-MP or
one after it, will support 46-bit physical address, may be, even 48
bit. And what would happen 10 years from now, when 48 bit (current
physical address limitation of AMD64 instruction set) runs out of gas?
Nothing dramatic, really. They will introduce new page table format.
Of course, old OS versions will be screwed, but new OS versions will
be adapted to new format with minimal difficulties.
Yes, for Itanium crossing of 256TB limit would be smoother (assuming
Itanium survives that long), but in great scheme of things the
difference hardly matters.