Extended Memory 64-bit Technology (EM64T) is
Intel's implementation of
AMD64, a 64-bit extension to the
IA-32 architecture. See the
AMD64 article for architectural details.
History
The history of the EM64T project is long and convoluted, mainly due to the internal politics of
Intel. It began with the codename
Yamhill, named after a
Northern Oregon county. After several years of denying that this project existed, Intel eventually admitted it existed in early 2004, and gave it the codename CT (Clackamas Technology), where
Clackamas County is adjacent to Yamhill County. Then within the space of weeks of the CT announcement, Intel gave it several new names. After the spring 2004
IDF, Intel named it IA-32E (
IA-32 Extensions) and a few weeks later devised the name EM64T. Intel's chairman, Craig Barrett, admitted that this was one of their worst kept secrets.
Intel CPUs with EM64T
Intel's first processor to actively implement the EM64T technology is the processor codenamed
Nocona, and is being sold as Intel's latest dual-processor capable
Xeon. Since the Xeon itself is directly based on Intel's desktop processor, the Pentium 4, the Pentium 4 also has EM64T technology built in, although as with
Hyper-Threading, this feature was not initially enabled on the then-new
Prescott design, likely because Intel had not yet perfected it at the time. Intel has since begun selling EM64T enabled Pentium 4's using the E0 revision of the Prescott core, being sold on the market as the Pentium 4, model F. The E0 revision also adds eXecute Disable(XD) support to EM64T, Intel's name for the
NX bit, and should be backported in to the Nocona design soon.
See also
External links
This article is licensed under the GNU Free Documentation License.
