(micro) processors are machines that execute instructions and
act on data. the format and interpretation of these instructions
are machine dependant - that is to say that a particular binary
string of one's and zero's mean specific thiing(s) to each
processor design or architecture. also microprocessors address
memory with a parallel bus - the width of that bus dictates the
speed and the amount of addressable memory that is possible.
that said comtemporary Intel processors adhere to either a 32
bit or 64 bit architecture. Those earlier processors comforming to
32 bits of internal processing/memory capacity adhere to Intel's
ia-32 (Intel architecture - 32 bits). It follows then that ia-64 is
their 64 bit variant - a new architecture found in their itanium
series. ia-64 machines can at best only emulate ia-32 code and do
so in software thus do so s-l-o-w-l-y.
with the market pressures inflicted by Intel's rival amd (and
their 64 bit architecture capable of executing both in 32 and/or 64
bit modes) Intel had to devise a 64 bit extension to the ubiquitous
ia-32. amd's 32 bit execution is rendered in hardware and thus a
competitive performer any ia-32 machine. moreover amd's design is
more than patching or streching 32 bit registers to 64 bits. not
being capable of bringing themselves to acknowledge amd's
innovation they (Intel) call their extension to ia-32 (and again I
do mean extension not a re-architecture) em64t for extended memory
architecture 64 bit technology - it is supposed to adhere to amd's
amd64.
amd's "glue-less" architecture, btw, (namely on-die memory mgt
unit along with hypertransport interconnect) blows intels aging
front-side bus architecture away - big time (particularly as you
increase the number of processors in the system design. amd's
design was also created with dual-core laid out from the start
though dual-core designs have only recently been introduced into
the marketplace (ahead of schedule).
when comparing ia-32 to amd64 machines don't get side-tracked by
processor clock speed either. amd's design allows them to run at
slower clock speed (and thus cooler) yet meet or exceed ia-32
performance.
hope this helps a bitrc
