[Info-vax] RealWorldTech on Poulson

[John Wallace]

On Jul 3, 3:45 pm, JF Mezei <jfmezei.spam... at vaxination.ca> wrote:
> Neil Rieck wrote:
> > As I understand the current debacle, EPIC relied on advances in
> > complier technology which never occurred.
>
> How can a compiler predict how a data processing program will execute
> since the compiler doesn't have any idea what data will be processed ?
>
> Compilers can do wonderful things when a program calculates pi to
> infinite  precision since the logic is fixed and the copiler can really
> optimise it. But for situations wherethe flow of the program depends on
> the data being processed (data to which the compiler does not have
> access), then EPIC can't rely on compiler advances.
>
> The Alpha presentations pre-June-25-2001 that showed why IA64 would not
> work are still valid today.
>
> If you gave the 8086 as big a cache as IA64 gets, how much better would
> the 8086 be compared to IA64 ?
>
> At the end of the day, IA64 gets palatable performance due to brute force.
>
> > Personal comment: I think Intel and HP are currently at a critical
> > point where the next few decisions will allow the Itanium program to
> > "take flight and dominate the enterprise  market" or crash.
>
> A rolling stone gathers no moss. Converting IA64 to a normal chip with
> the advanced features found on competing platforms will liekly take a
> couple of iterations during whic the platform will be in a state of
> flux, with customers not too happy with performance unless they have to
> recompile/recertify all their applications.
>
> And while Intel/HP are touting Poulson as the next best thing since
> sliced bread, lets not forget that the 8086 is not be idle and by the
> time Poulson comes out, the 8086 may have even widened the gap between
> itself and IA64.
>
> > As far as HP is concerned, PA-RISC
> > and Alpha are gone so the death of Itanium would hurt them.
>
> The plans set forth by LaCarly may contiue: move enterprise computing to
> commodity hardware. HP will just need to move its OS to the 8086 and
> focus on building a full range of industry standard servers intluding
> big iron.
>
> When you compare the costs of developping IA64 and its compilers, it may
> end up being much cheaper to port HP-UX/NSK and perhaps even VMS to the
> 8086 and use existing compilers for that platform.

"If you gave the 8086 as big a cache as IA64 gets, how much better
would
the 8086 be compared to IA64 ? "

A very very fair question, to which we probably won't be told the
answer. But IA64 chips are basically a big cache with a weird
processor tacked on.

I'll perhaps have more to say on this subject on a bit, in particular
wrt the accuracy and relevance of "x86 microprocessors rely on snoop-
based cache coherency; <snip> In contrast, Tukwila and Poulson have a
directory-based coherency protocol that scales much better ...
<snip> ... For a 4 or 16 socket system, the bandwidth savings are
huge."