[ Thanks to Augustus for this link.
]
“Intel’s new processor’s claim to fame is Intel’s new EM64T
architecture which aims to bring 64-bit processing and 64-bit
memory addressing to the x86 architecture while still maintaining
32-bit compatibility. What does this mean exactly? Well, all
previous 32-bit processors from Intel only support running 32-bit
applications under a 32-bit operating system. Intel calls this
IA-32 mode. With the EM64T architecture, Intel has enabled what
they call IA-32e mode. This mode either allows you to run 64-bit
application under a 64-bit OS or even 32-bit applications under a
64-bit OS. In 64-bit mode, your addressable memory addressing goes
from 4 Gigabytes max to 16 Exabytes (17,179,869,184 GB) max, which
makes enterprise customers very happy since, in some situations,
4GB won’t cut it…”