p4 v itinium

[Josh Fryman]

> So if you require 4 GBytes of memory per node, I would expect the IA64 
> systems to roughly equal the Pentium 4 at some additional cost. Other 
> 64-bit architectures to look at would be the IBM Power 4 and the Alpha 
> EV6 and EV7 (expected to be release in Q4 2002).

sure.  the P4 can go over 4GB per process (well, 3.5GB under linux with
patch from AA) and the systems will support > 4GB RAM.  the problem is
that to go over the 4GB space, you have to use the PAE registers and do
your own version of the old segment-offset page system.  this requires a
lot of work.  in short, the Px series is only viable for 32-bit address
limits.  to go beyond it isn't worth the headache, performance hits, and
various unknowns.

native 64-bit platforms would be much better to work with if you need
this kind of memory available.  while i think the alpha is a great
platform, it has an unknown future.  samsung with manufacture the 364
series, but beyond that... who knows.  Power4 and (ahem) Sparc are 
possible options as well.  i try to avoid sparc for cost reasons, but
if you really need the memory...

a better question is why a single node needs that kind of memory for an
application?  seems like you'd be better off breaking it up under a real
parallel process situation.

-josh