EM64T (Intel 64)

Extended Memory 64 Technology is more commonly known as em64t or Intel 64. Today, this 64-bit extension is used in several Intel processors including the following:

  • Pentium 4
  • Pentium D
  • Pentium Extreme Edition
  • Xeon
  • Celeron D
  • Core 2 processors
  • Pentium Dual-Core

EM64T was first introduced to the market way back in 2004. First known as Yamhill, this technology underwent several name changes before finally settling on EM64T in time for its formal announcement in 2004.

Starting 2006 however, Intel no longer referred to this technology by that name and is now using Intel 64. The change of name was supposed to be for competitive measures in the market over its rival AMD64.

This technology was first tested on the E revision of Pentium 4 in June 2004. For Intel products, Nocona (also known as Xeon) was the first to adopt the Intel 64 technology. Thus, it gives testament to the idea that Intel 64 technology is also supported by Pentium 64 unlike results shown in the Prescott design.

Moreover, for desktop processors, EM64T was initially tried on the N0 Stepping Prescott-2M. The revised version of the technology now includes support for Execute Disable (XD). Lastly, for the mobile processors, Intel 64 for Merom of Core 2 processors was released on July 2006.


First things first, you can only use the EM64T with a 64-bit operating system. However, if you do run this technology, you can avail of the following benefits:

  • You can install a maximum of 16 exabytes of RAM
  • You can execute 8-bit operations since most 64-bits follow the same scheme
  • There is a new 64-bit pointer in place for the EIP (for the 32-bits), which is the RIP and that in itself also now has its own relative address.

Other Features

There are also peculiarities involved with using such large amounts of memory for your processors. For instance, because the EM64T processor corresponds to the x86-64 ABI, the objects stored are filed according to three: small, medium, or large.

  • Objects stored in a small memory model have only 2GB of total space to use (for both code and data).
  • Models with medium memory have 2GB for the code section and there is 64-bit addressing for the data.
  • Lastly, the large model allows both data and code into a memory larger than 2GB.