[Gllug] IA32? IA64? x86...

[Avtar Marwaha]

On Thu, 2002-10-03 at 11:09, Dylan wrote:
> Hi guys
> 
> I'm getting a bit fuddled here...
> 
> Can one of the hardware gurus explain what's what? Which processors are IA32 
> (i{3|4|5}86?), which IA64? Where does i686 fit in the scheme? How is the 
> Itanium related (if at all?)

IA32 means Intel Architecture 32 (bit).  It is the name for the 32 bit
CPU instruction set, it is this instruction set which allows all PC CPUs
to uses the same executables.  All the PC chips since the 386 have been
compatible with this instruction set.  The i686 would have been Pentium
pro/pentium2/pentium3 family, but Intel decided to give the chips names 
They all use the same core, but have had modifications made to make them
run faster, ad at higher clock speeds.  i786 is the pentium 4 family.

One of the problems with IA32 is that it is not the best instruction
set, and making a chip compatible with IA32 restricts the performance of
chips in some areas.  The best example is floating point performance,
other chips which use other instruction sets like Motorola chips used in
Macs have much better performance for the same clock speed.  Intel
recently introduced SSE2 to try to get around this problem.

Itanium uses a completely different instruction set called EPIC
(Explicitly Parallel Instruction Computing), which is a brand new
instruction set and isn't compatible with IA32.  Intel would have liked
this to be the new architecture that all PC evolved to.  The Itanium was
based on this instruction set and it was aimed at the server market, but
they have not done very well.  I remember reading that Intel has sold
less than 1000 of these chips since their launch.  Itanium 2 has
recently been released, but i dont know how well it is doing, or what
the differences are between it and Itanium 1.

AMD have decided to extend the 32bit IA32 into a 64 bit IA64.  There are
probably lots of other improvements but I don't know what they are. 
However, IA64 is computable with IA32, so you can run executable that
you have now on the new chips.  The chips AMD is building based on are
code named hammer, and a chip has been announced called AMD Opteron, it
is aimed at the server market, and looks to be released around the
beginning of next year.

HTH

Avtar



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