Gecko's CPU Library

Intel Pentium 4 (Willamette) processors

Introduction: November 2000


The Pentium 4 brand refered to Intel's line of single-core mainstream desktop and laptop central processing units (CPUs) introduced on November 20, 2000 (August 8, 2008 was the date of last shipments of Pentium 4s). They had the 7th-generation architecture, called NetBurst, which was the company's first all-new design since 1995, when the Intel P6 architecture of the Pentium Pro CPUs had been introduced. NetBurst differed from the preceding Intel P6 - of Pentium III, II, etc. - by featuring a very deep instruction pipeline to achieve very high clock speeds (up to 4GHz) limited only by max. power consumption (TDP) reaching up to 115W in 3.6–3.8GHz Prescotts and Prescotts 2M (a high TDP required an additional cooling that was noisy or expensive). In 2004, the initial 32-bit x86 instruction set of the Pentium 4 microprocessors was extended by the 64-bit x86-64 set.

Pentium 4 CPUs introduced the SSE2 and SSE3 instruction sets to accelerate calculations, transactions, media processing, 3D graphics, and games. They also integrated Hyper-threading (HT), a feature to make one physical CPU work as two logical and virtual CPUs. The Intel's flagship Pentium 4 also came in a low-end version branded Celeron (often referred to as Celeron 4), and a high-end derivative, Xeon, intended for multiprocessor servers and workstations.

The Pentium 4 had an IHS (Integrated Heat Spreader) that prevented the CPU core from accidentally getting damaged when mounting and unmounting cooling solutions. Prior to the IHS, a CPU shim was sometimes used by people worried about damaging the core. Overclockers sometimes removed the IHS on Socket 478 chips to allow for more direct heat transfer. However, on LGA775 chips the IHS was directly welded to the processor core, meaning that the IHS cannot be removed without irreparably damaging the processor.

In 2005, the Pentium 4 was superseded by the Pentium D and Pentium Extreme Edition dual-core CPUs.

The Willamette core

Willamette, project code name for the first Pentium 4 architecture implementation, experienced long delays in completion of its design process. The project was started in 1998, when Intel saw the Pentium II as their permanent line. At that time, the Willamette core was expected to operate at frequencies of around 1GHz, maximum. However, Willamette release delays saw the introduction of the Pentium III prior to its completion. Since the radical differences in these architectures meant Intel could not market Willamette as a Pentium III, it was named Pentium 4.

In November 2000, Intel released the Willamette-based Pentium 4 at speeds of 1.4 and 1.5GHz. Most industry experts regarded the initial release as a stopgap product, introduced before it was truly ready. According to these experts, the Pentium 4 was released because the competing Thunderbird-based AMD Athlon was outperforming the aging Pentium III, and further improvements to the P-III were not yet possible. This Pentium 4 was produced using a 0.18 micrometer (180 nm) process and initially used Socket 423, with later revisions moving to Socket 478. These variants were identified by the Intel product codes 80528 and 80531 respectively.

On the test bench, the Willamette was somewhat disappointing to analysts in that not only was it unable to outperform the Athlon and the highest-clocked Pentium IIIs in all testing situations, it was not clearly superior to even the budget segment's AMD Duron. Although introduced at a price of US$819 (in 1000 unit quantities), it sold at a modest but respectable rate, handicapped somewhat by the requirement of relatively expensive Rambus Dynamic RAM (RDRAM). The Pentium III remained Intel's top selling chip, with the Athlon also selling slightly better than the Pentium 4.

In January 2001, a still slower 1.3GHz model was added to the range, but over the next twelve months, Intel gradually started reducing AMD's leadership in performance. April 2001 brought the 1.7GHz P4, the first one to provide performance clearly superior to the old Pentium III. July saw 1.6 and 1.8GHz models and in August 2001, Intel released 1.9 and 2.0GHz Pentium 4s. In the same month, they released the 845 chipset that supported much cheaper PC133 SDRAM instead of RDRAM. While SDRAM was much slower than RDRAM and severely hampered the bandwidth-hungry Pentium 4, the fact that it was so much cheaper caused the Pentium 4's sales to grow considerably. The new chipset allowed the P4 to displace the Pentium III virtually overnight, becoming the top-selling processor on the market.

The Willamette code name was derived from the Willamette Valley region of Oregon, where a large number of Intel manufacturing facilities were located.

Source: Wikipedia, the free encyclopedia.