Pentium 4 Gets 64-bit And Another Core

In 2005, Intel improved its Pentium 4 twice. First, with the Prescott-2M, and then with Smithfield. The former was a 64-bit processor, based on the Prescott design, and the latter was a dual-core processor. They are fairly similar and have the same problems as other Pentium 4s: low instructions per cycle (IPC) throughput and difficulty in increasing the clock frequency due to current losses. These two processors, intended to limit losses while awaiting the Core 2 Duo, are not among Intel’s most highly regarded. And while the Pentium D (the commercial name of the Smithfield) does have two cores, in reality it’s an assembly of two Prescott dies in the same package.

An interesting point is that whereas the Pentium 4 processors intended for the consumer market did not use the PAE technology (which enables 36-bit, as opposed to 32-bit memory management) and were therefore limited to 4 GB of RAM, these models can go beyond that limit. In practice, the address bus is still limited to 36 bits (40 bits on the Xeon), but PAE (management in 4 GB pages) is now ancient history—a 64-bit program is capable of making full use of the available memory.

Hyper-Threading, an Intel SMT technology, was available on certain models (Xeon and Extreme Edition). Finally, a 65 nm version (the 9x0 series) of the Pentium 4 was released later, but made no major improvements.