EM what ??

Intel Extended Memory 64 Technology (Intel EM64T) enables 64-bit computing on the server/workstation and desktop platforms when combined with supporting software. Intel EM64T improves performance by allowing the system to address more than 4 GB of both virtual and physical memory.

Technically speaking, EM64T offers to intel processors what x86-64 offers to AMD processors. Ancient disagreements such as 3Dnow-vs-SSE still holds, but the rest should be exactly the same. It is supported by latest XEON processors.

Intel EM64T provides support for:

Currently physical addresses are restricted to 40 bits, and linear addresses are restricted to 48 bits, sign-extended.

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See the "Tell me about x86 64 bits CPU" page for more details.