Intel® Extended Memory 64 Technology is one of a number of innovations being added to Intel's IA-32 Server and Workstation platforms in 2004 and desktop processors in 2005. It represents a natural addition to Intel's IA-32 architecture, allowing platforms to access larger amounts of memory. Processors with Intel® EM64T will support 64-bit extended operating systems from Microsoft, Red Hat and SuSE. Processors running in legacy* mode remain fully compatible with today's existing 32-bit applications and operating systems. (Note: EM64T is not compatible with Itanium processor architecture or software.)

EM64T has three modes. The modes are NOT selectable but determined by the processor itself based on the proper support of installed components such as EM64 enabled BIOS, drivers, OS, and applications. The modes are:

1 - Legacy Mode = 32-bit O/S and 32-bit applications: No software changes are required; however the user gets no benefit from Intel® EM64T

2 - IA-32e = Compatibility Mode = 64-bit O/S and 32-bit applications: This usage requires all 64-bit device drivers. In this mode, the O/S will see the 64-bit extensions, but the 32-bit application will not. Existing 32-bit applications do not need to be recompiled, and may or may not benefit from the 64-bit extensions. The application will likely need to be recertified by the vendor to run on the new 64-bit extended O/S

3 - IA -32 = 64-bit Mode = 64-bit O/S and 64-bit applications: This usage requires 64-bit device drivers. It also requires applications to be modified for 64-bit operation and then recompiled and validated

SuSE Linux, Redhat and Microsoft will all offer 64-bit support Operating Systems for the new XEONS starting in second half of 2004. Microsoft currently has BETA preview version available for testing downloads. Here are the links (compatibility is not guaranteed):

http://www.microsoft.com/windowsserver2003/64bit/extended/trial/default.mspx (Server 2003)

http://www.microsoft.com/windowsxp/64bit/evaluation/upgrade.mspx (Windows XP)