Pentium 4 processors have an
integrated heat spreader (IHS) that prevents the die from accidentally being damaged when mounting and unmounting cooling solutions. Prior to the IHS, a
CPU shim was some times used by people worried about damaging the core. Overclockers sometimes removed the IHS from Socket 423 and Socket 478 chips to allow for more direct heat transfer. On Socket 478 Prescott processors and processors using the Socket LGA 775 (Socket T) interface, the IHS is directly soldered to the die or dies, making it difficult to remove.
Willamette Willamette, the project codename for the first NetBurst microarchitecture implementation, experienced long delays in the 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 up to about 1 GHz. However, the
Pentium III was released while Willamette was still being finished. Due to the radical differences between the
P6 and NetBurst microarchitectures, Intel could not market Willamette as a Pentium III, so it was marketed as the Pentium 4. On November 20, 2000, Intel released the Willamette-based Pentium 4 clocked at 1.4 and 1.5 GHz. 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 Pentium III were not yet possible. This Pentium 4 was produced using a 180 nm process and initially used
Socket 423 (also called socket W, for "Willamette"), with later revisions moving to
Socket 478 (socket N, for "Northwood"). 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, but it was not superior to the budget segment's
AMD Duron. Although introduced at prices of $644 (1.4 GHz) and $819 (1.5 GHz) for 1000 quantities to OEM PC manufacturers (prices for models for the consumer market varied by retailer), it sold at a modest but respectable rate, handicapped somewhat by the requirement for relatively fast yet expensive Rambus Dynamic RAM (
RDRAM). The Pentium III remained Intel's top selling processor line, with the Athlon also selling slightly better than the Pentium 4. While Intel bundled two RDRAM modules with each boxed Pentium 4, it did not facilitate Pentium 4 sales and was not considered a true solution by many. In January 2001, a still slower 1.3 GHz model was added to the range, but over the next twelve months, Intel gradually started reducing AMD's leadership in performance. In April 2001 a 1.7 GHz Pentium 4 was launched, the first model to provide performance clearly superior to the old Pentium III. July saw 1.6 and 1.8 GHz models and in August 2001, Intel released 1.9 and 2 GHz Pentium 4s. In the same month, they released the
845 chipset that supported much cheaper
PC133 SDRAM instead of RDRAM. The fact that SDRAM was so much cheaper caused the Pentium 4's sales to grow considerably. Northwood (product code 80532) combined an increase in the
L2 cache size from 256 KB to 512 KB (increasing the transistor count from 42 million to 55 million) with a transition to a new
130 nm fabrication process. The 3.06 GHz Pentium 4 enabled
Hyper-Threading Technology that was first supported in Foster-based Xeons. This began the convention of virtual processors (or virtual cores) under x86 by enabling multiple threads to be run at the same time on the same physical processor. By shuffling two (ideally differing) program instructions to simultaneously execute through a single physical processor core, the goal is to best utilize processor resources that would have otherwise been unused from the traditional approach of having these single instructions wait for each other to execute singularly through the core. This initial 3.06 GHz 533FSB Pentium 4 Hyper-Threading enabled processor was known as Pentium 4 HT and was introduced to mass market by Gateway in November 2002. On April 14, 2003, Intel officially launched the new Pentium 4 HT processor. This processor used an 800 MT/s FSB (200 MHz physical clock), was clocked at 3 GHz, and had Hyper-Threading technology. This was meant to help the Pentium 4 better compete with AMD's
Opteron line of processors. Meanwhile, with the launch of the Athlon XP 3200+ in AMD's desktop line, AMD increased the Athlon XP's FSB speed from 333 MT/s to 400 MT/s, but it was not enough to hold off the new 3 GHz Pentium 4 HT. The Pentium 4 HT's increase to a 200 MHz quad-pumped bus (200 x 4 = 800 MHz effective) greatly helped to satisfy the bandwidth requirements the NetBurst architecture desired for reaching optimal performance. While the Athlon XP architecture was less dependent on bandwidth, the bandwidth numbers reached by Intel were well out of range for the Athlon's EV6 bus. Hypothetically, EV6 could have achieved the same bandwidth numbers, but only at speeds unreachable at the time. Intel's higher bandwidth proved useful in benchmarks for streaming operations, and Intel marketing wisely capitalized on this as a tangible improvement over AMD's desktop processors. Northwood 2.4 GHz, 2.6 GHz and 2.8 GHz variants were released on May 21, 2003. A 3.2 GHz variant was launched on June 23, 2003 and the final 3.4 GHz version arrived on February 2, 2004. Overclocking early stepping Northwood cores yielded a startling phenomenon. While core voltage approaching 1.7 V and above would often allow substantial additional gains in overclocking headroom, the processor would slowly (over several months or even weeks) become more unstable over time with a degradation in maximum stable clock speed before dying and becoming totally unusable. This became known as
Sudden Northwood Death Syndrome (SNDS), which was caused by
electromigration.
Pentium 4 M Also based on the Northwood core, the
Mobile Intel Pentium 4 Processor – M (also known as the
Pentium 4 M) was released on April 23, 2002, and included Intel's
SpeedStep and Deeper Sleep technologies. Its
TDP is about 35 watts in most applications. This lowered power consumption was due to lowered core voltage, and other features mentioned previously. All mobile variants of the Pentium 4 have an exposed CPU die without the IHS.
Mobile Pentium 4 The
Mobile Intel Pentium 4 Processor (known simply as the
Mobile Pentium 4) was released to address the problem of putting a full desktop Pentium 4 processor into a laptop, which some manufacturers were doing. The Mobile Pentium 4 used a 533 MT/s FSB, following the desktop Pentium 4's evolution. Oddly, increasing the bus speed by 133 MT/s (33 MHz) caused a massive increase in TDPs, as mobile Pentium 4 processors emitted 59.8–70 W of heat, with the Hyper-Threading variants emitting 66.1–88 W. This allowed the mobile Pentium 4 to bridge the gap between the desktop Pentium 4 (up to 115 W TDP), and the Pentium 4 M (up to 35 W TDP). Early versions were based on the Northwood core with 512 KB L2 cache, while the later Hyper-Threading versions were based on the Prescott core with 1 MB L2 cache. Intel's naming conventions made it difficult at the time of the processor's release to identify the processor model. There were approximately four mobile Intel processor models available at the same time; these include the
Mobile Pentium III M, the Pentium 4 M, the Mobile Pentium 4, and the more power and performance-efficient
Pentium M.
Northwood (Extreme Edition) In September 2003, at the Intel Developer Forum, the Pentium 4 Extreme Edition (P4EE) was announced, just over a week before the launch of
Athlon 64 and
Athlon 64 FX. The design was mostly identical to Pentium 4 (to the extent that it would run in the same motherboards), but differed by an added 2 MB of level 3 cache. It shared the same Gallatin core as the Xeon MP, though in a Socket 478 form factor (as opposed to Socket 603 for the Xeon MP) and with an 800 MT/s bus, twice as fast as that of the Xeon MP. While Intel maintained that the Extreme Edition was aimed at gamers, critics viewed it as an attempt to steal the Athlon 64's launch thunder, nicknaming it the "Emergency Edition". With a price tag of $1000, it was also referred to as the "Expensive Edition" and "Extremely Expensive". The added cache generally resulted in a noticeable performance increase in most processor intensive applications. Multimedia encoding and certain games benefited the most, with the Extreme Edition outperforming the Pentium 4, and even the two Athlon 64 variants, although the lower price and more balanced performance of the Athlon 64 (particularly the non-FX version) led to it usually being seen as the better value proposition. Nonetheless, the Extreme Edition did achieve Intel's apparent aim, which was to prevent AMD from being the performance champion with the new Athlon 64, which was winning every single major benchmark over the existing Pentium 4s. In January 2004, a 3.4 GHz version was released for Socket 478, and in Summer 2004 the CPU was released using the new Socket 775 (
LGA 775). A slight performance increase was achieved in late 2004 by increasing the bus speed from 800 MT/s to 1066 MT/s, resulting in a 3.46 GHz Pentium 4 Extreme Edition. By most metrics, this was on a per-clock basis the fastest single-core NetBurst processor that was ever produced, even outperforming many of its successor chips (not counting the dual-core Pentium D). Afterwards, the Pentium 4 Extreme Edition was migrated to the Prescott core. The new 3.73 GHz Extreme Edition had the same features as a 6x0-sequence Prescott 2M, but with a 1066 MT/s bus. In practice however, the 3.73 GHz Pentium 4 Extreme Edition almost always proved to be slower than the 3.46 GHz Pentium 4 Extreme Edition, which is most likely due to the lack of an L3 cache and the longer instruction pipeline. The only advantage the 3.73 GHz Pentium 4 Extreme Edition had over the 3.46 GHz Pentium 4 Extreme Edition was the ability to run 64-bit applications since all Gallatin-based Pentium 4 Extreme Edition processors lacked the Intel 64 (then known as EM64T) instruction set. Although never a particularly good seller, especially since it was released in a time when AMD was asserting near total dominance in the processor performance race, the Pentium 4 Extreme Edition established a new position within Intel's product line, that of an enthusiast oriented chip with the highest-end specifications offered by Intel chips, along with unlocked multipliers to allow for easier overclocking. In this role it has since been succeeded by the
Pentium Extreme Edition (The Extreme version of the dual-core
Pentium D), the
Core 2 Extreme, the
Core i7 and the
Core i9. Contrary to popular belief, however, the Socket 478 versions of the Pentium 4 Extreme Edition CPUs such as the Gallatin-based Pentium 4 Extreme Edition for Socket 478 all have a locked multiplier, meaning that they are not overclockable unless the
front-side bus speeds are increased (which runs the potential risks of erratic behaviors such as reliability and stability issues). Only the Socket 775/LGA 775 versions of the Pentium 4 Extreme Edition, as well as the Pentium Extreme Edition (Smithfield) and Engineering Sample CPUs have unlocked multipliers.
Prescott On February 1, 2004, Intel introduced a new core codenamed Prescott. The core used the
90 nm process for the first time, which one analyst described as "a major reworking of the Pentium 4's microarchitecture." Despite this overhaul, the performance gains were inconsistent. Some programs benefited from Prescott's doubled cache and SSE3 instructions, whereas others were harmed by its longer pipeline. The Prescott's microarchitecture allowed slightly higher clock speeds, but not nearly as high as Intel had anticipated. The fastest mass-produced Prescott-based Pentium 4s were clocked at 3.8 GHz. While Northwood ultimately achieved clock speeds 70% higher than Willamette, Prescott only scaled 12% beyond Northwood. Prescott's inability to achieve greater clock speeds was attributed to the very high power consumption and heat output of the processor. This led to the processor receiving the nickname "PresHot" on forums. In fact, Prescott's power and heat characteristics were only slightly higher than those of Northwood of the same speed and nearly equal to the Gallatin-based Extreme Editions, but since those processors had already been operating near the limits of what was considered thermally acceptable, this still posed a major issue. The release of Prescott also coincided with the launch of
LGA 775 and the
BTX form factor, which were also criticized. Tests showed that a given Pentium 4 made for LGA 775 consumed more power and produced more heat than the exact same chip in a socket 478 package. The BTX form factor, meanwhile, showed signs of having been designed for the sole purpose of managing the Prescott's heat output at the expense of other components and concerns, such as blowing hot air from the CPU directly into the graphics card's heatsink/fan. These magnified the perception of Prescott as an excessively hot chip. The Prescott Pentium 4 contains 125 million transistors and has a die area of 112 mm2. It was fabricated in a 90 nm process with seven levels of
copper interconnect. However, they were later made available to the general public as the 5x1 series. A number of low-end Intel 64-enabled Prescotts, with 533 MHz FSB speed, were also released. The E0 stepping of the Prescott series introduced the
XD bit feature. This technology, introduced to the x86 architecture by AMD as
NX (No eXecute), can help prevent certain types of malicious code from
exploiting a
buffer overflow to get executed. Models supporting XD bit include the 5x0J and 5x1 series as well as the low-end 5x5J and 5x6. The Prescott processors are the first to support
SSE3, along with all
Pentium D processors.
Prescott 2M (Extreme Edition) Intel, by the first quarter of 2005, released a new Prescott core with 6x0 numbering, codenamed Prescott 2M. It is also sometimes known by the name of its
Xeon derivative, Irwindale. It features Hyper-Threading,
Intel 64, the XD bit,
EIST (Enhanced Intel SpeedStep Technology),
Thermal Monitor 2 (for processors at 3.6 GHz and above), and 2 MB of L2 cache. However, AnandTech found that this resulted in 17% higher cache latency compared to Prescott, which combined with the lack of consumer-targeted programs requiring more cache, largely negated the advantage that added cache introduced. Rather than being a targeted speed boost the double size cache was intended to provide the same space and hence performance for
64-bit mode operations, due to the doubled
word size compared to 32-bit mode. On November 14, 2005, Intel released Prescott 2M processors with VT (
Virtualization Technology, codenamed Vanderpool) enabled. Intel only released two models of this Prescott 2M category: 662 and 672, running at 3.6 GHz and 3.8 GHz, respectively.
Cedar Mill The final revision of the Pentium 4 was
Cedar Mill, released on January 5, 2006. This was a die shrink of the Prescott-based 600 series core to
65 nm, with no real feature additions but significantly reduced power consumption. The Cedar Mill is closely linked to the
Pentium D Presler revision, with each Presler CPU consisting of two Cedar Mill cores on the same chip package. Cedar Mill had a lower heat output than Prescott, with a
TDP of 86 W. The D0 stepping in late 2006 reduced this to 65 watts. It has a 65 nm core and features the same 31-stage pipeline as Prescott, 800 MT/s FSB,
Intel 64,
Hyper-Threading, but no
Virtualization Technology. As with Prescott 2M, Cedar Mill also has a 2 MB L2 cache. Intel initially announced four
VT-x enabled Cedar Mill processors with model numbers 633 to 663, but these were later cancelled and replaced by models 631 to 661 without VT-x, the extra 1 added to the model number distinguishing them from the 90 nm Prescott cores operating at the same frequencies. Cedar Mill processors ranged in frequency from 3.0 to 3.6 GHz, down from the 3.8 GHz maximum of the Prescott-based 670 and 672. Overclockers managed to exceed 8 GHz with these processors using liquid nitrogen cooling. The name "Cedar Mill" refers to
Cedar Mill, Oregon, an
unincorporated community near Intel's
Hillsboro, Oregon facilities. ==Successor==