Pentium 4

Pentium 4

File:Pentium4ds.jpg
General information
Launched	2000
Discontinued	2008
Common manufacturer	Intel
Performance
Max. CPU clock rate	1.3 GHz to 3.8 GHz
FSB speeds	400 MT/s to 1066 MT/s
Architecture and classification
Technology node	180 nm to 65 nm
Microarchitecture	NetBurst
Instruction set	x86 (i386), x86-64, MMX, SSE, SSE2, SSE3
Physical specifications
Sockets	Socket 423 Socket 478 LGA 775
Products, models, variants
Core names	Willamette Northwood Prescott Cedar Mill

The Pentium 4 brand refers to Intel's line of single-core desktop and laptop central processing units (CPUs) introduced on November 20, 2000 and shipped through August 8, 2008. They had the 7th-generation x86 microarchitecture, called NetBurst, which was the company's first all-new design since introduction of P6 microarchitecture of the Pentium Pro CPUs in 1995. NetBurst differed from the preceding P6 (Pentium III, II, etc.) by featuring a very deep instruction pipeline to achieve very high clock speeds (up to 3.8 GHz) limited only by TDPs reaching up to 115 W in 3.4 GHz –3.8 GHz Prescott and Prescotts 2M cores . In 2004, the initial 32-bit x86 instruction set of the Pentium 4 microprocessors was extended by the 64-bit x86-64 set.

The first Pentium 4 cores, codenamed Willamette, were clocked from 1.3 GHz to 2 GHz and the first Willamette processor was released on November 20, 2000 using Socket 423. Notable with the introduction of the Pentium 4 was the 400 MHz FSB. It actually operated at 100 MHz but the FSB was quad-pumped, meaning that the maximum transfer rate was four times the base clock of the bus, so it was considered to run at 400 MHz. The AMD Athlon's double-pumped FSB was running at 200 MHz or 266 MHz at that time. I AM A STUD I TRULY AM

Pentium 4 CPUs introduced the SSE2 and, in the Prescott-based Pentium 4s, SSE3 instruction sets to accelerate calculations, transactions, media processing, 3D graphics, and games. Later versions featured Hyper-Threading Technology (HTT), a feature to make one physical CPU work as two CPUs, one logical and one virtual. Intel also marketed a version of their low-end Celeron processors based on the NetBurst microarchitecture (often referred to as Celeron 4), and a high-end derivative, Xeon, intended for multiprocessor servers and workstations. In 2005, the Pentium 4 was complemented by the Pentium D and Pentium Extreme Edition dual-core CPUs.

Microarchitecture

In benchmark evaluations, the advantages of the NetBurst microarchitecture were not clear. With carefully optimized application code, the first Pentium 4s did outperform Intel's fastest Pentium III (clocked at 1.13 GHz at the time), as expected. But in legacy applications with many branching or x87 floating-point instructions, the Pentium 4 would merely match or even fall behind its predecessor. Its main handicap was a shared unidirectional bus. Furthermore, the NetBurst microarchitecture gave off more heat than any previous Intel or AMD microarchitectures.

As a result, the Pentium 4's introduction was met with mixed reviews: Developers disliked the Pentium 4, as it posed a new set of code optimization rules. For example, in mathematical applications AMD's lower-clocked Athlon (the fastest-clocked model was clocked at 1.2 GHz at the time) easily outperformed the Pentium 4, which would only catch up if software were re-compiled with SSE2 support. Tom Yager of Infoworld magazine called it "the fastest CPU - for programs that fit entirely in cache". Computer-savvy buyers avoided Pentium 4 PCs due to their price-premium and questionable benefit. In terms of product marketing, the Pentium 4's singular emphasis on clock frequency (above all else) made it a marketer's dream. The result of this was that the NetBurst microarchitecture was often referred to as a marchitecture by various computing websites and publications during the life of the Pentium 4.

The two classical metrics of CPU performance are IPC (instructions per cycle) and clock speed. While IPC is difficult to quantify (due to dependence on the benchmark application's instruction mix), clock speed is a simple measurement yielding a single absolute number. Unsophisticated buyers would simply consider the processor with the highest clock speed to be the best product, and the Pentium 4 was the undisputed megahertz champion. As AMD was unable to compete by these rules, it countered Intel's marketing advantage with the "megahertz myth" campaign. AMD product marketing used a "PR-rating" system, which assigned a merit value based on relative performance to a baseline machine.

See also: megahertz myth

A Pentium 4, clocked at 2.4 GHz

At the launch of the Pentium 4, Intel stated NetBurst-based processors were expected to scale to 10 GHz (which should be achieved over several fabrication process generations). However, the NetBurst microarchitecture ultimately hit a frequency ceiling far below that expectation – the fastest clocked NetBurst-based models reached a peak clock speed of 3.8 GHz. Intel had not anticipated a rapid upward scaling of transistor power leakage that began to occur as the die reached the 90 nm lithography and smaller. This new power leakage phenomenon, along with the standard thermal output, created cooling and clock scaling problems as clock speeds increased. Reacting to these unexpected obstacles, Intel attempted several core redesigns ("Prescott" most notably) and explored new manufacturing technologies, such as using multiple cores, increasing FSB speeds, increasing the cache size, and using a shorter, more efficient instruction pipeline along with lower clock speeds. Nothing solved their problems though and in 2003–05 Intel shifted development away from NetBurst to focus on the cooler-running Pentium M microarchitecture. On January 5, 2006, Intel launched the Core processors, which put greater emphasis on energy efficiency and performance per clock. The final NetBurst-derived products were released in 2007, with all subsequent product families switching exclusively to the Core microarchitecture. The NetBurst architecture was often affectionately referred to as NetBust.

Processor cores

The Pentium 4 has an integrated heat spreader (IHS) that prevents the die 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 423 and Socket 478 chips to allow for more direct heat transfer. However, on processors using the Socket LGA 775 (Socket T) interface, the IHS is directly soldered to the die(s), meaning that the IHS cannot be easily removed.

Intel Pentium 4 processor family
Desktop			Laptop
Code-named	Core	Date released	Code-named	Core	Date released
Willamette Northwood Prescott	180 nm 130 nm 90 nm	Nov 2000 Jan 2002 Mar 2004	Northwood	130 nm	Jun 2003
			Northwood Pentium 4-M	130 nm	Apr 2002
Hyper-threading (HT)
Northwood Prescott Prescott 2M Cedar Mill	130 nm 90 nm 90 nm 65 nm	May 2003 Feb 2004 Feb 2005 Jan 2006	Northwood Prescott	130 nm 90 nm	Sep 2003 Jun 2004
Gallatin XE Prescott 2M XE	130 nm 90 nm	Sep 2003 Feb 2005
List of Intel Pentium 4 microprocessors

Willamette

Pentium 4 Willamette 1.5GHz for Socket 423.

Pentium 4 Willamette 1.8GHz for Socket 478.

Willamette, the project codename for the first NetBurst microarchitecture 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 1 GHz, maximum. However, Willamette's release delays saw the introduction of the Pentium III prior to its completion. Due to the radical differences in the P6 and NetBurst microarchitectures, Intel could not market Willamette as a Pentium III, so it was marketed as 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 (a.k.a. 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 even clearly superior to even 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 condsidered a true solution by Anand Lal Shimpi of AnandTech, who stated in his review that the Pentium 4 needed a chipset that used a memory controller that could support DDR SDRAM.

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. 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 Pentium 4 to replace the Pentium III virtually overnight, becoming the top-selling mainstream processor on the market.

The Willamette code name is derived from the Willamette Valley region of Oregon, where a large number of Intel's manufacturing facilities are located.

Northwood

A 'Northwood' core Pentium 4 processor. Left the die, and right the heat spreader

In October 2001, the Athlon XP regained a clear lead for AMD, but in January 2002, Intel released Pentium 4s with their new Northwood core at 1.6 GHz, 1.8 GHz, 2 GHz and 2.2 GHz. 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. By making the processor out of smaller transistors, processors can run at higher clock speeds or at the same speed while producing less heat. In the same month, a version of the 845 chipset was released with support for DDR SDRAM, which provided double the bandwidth of PC133 SDRAM.

A 2.4 GHz Pentium 4 was released on April 2, 2002, and the bus speed increased from 400 MHz to 533 MHz for the 2.26 GHz, 2.4 GHz, and 2.53 GHz models in May, 2.66 GHz and 2.8 GHz models in August, and 3.06 GHz model in November. With Northwood, the Pentium 4 came of age. The battle for performance leadership remained competitive (as AMD introduced faster versions of the Athlon XP) but most observers agreed that the fastest-clocked Northwood-based Pentium 4 was usually ahead of its rival. This was particularly so in the summer of 2002, when AMD's changeover to a 130 nm production process did not help the Thoroughbred-based Athlon XP CPUs clock high enough to overcome the advantage of Pentium 4s in the 2.4 to 2.8 GHz range.

The 3.06 GHz Pentium 4 acquired Hyper-Threading Technology that first appeared in Foster-based Xeon, enabling multiple threads to be run at the same time by fitting them into otherwise unused spots in the instruction pipeline. The processor was not branded as Pentium 4 HT, which would be released later.

On April 14, 2003, Intel launched the new Pentium 4 HT processor. This processor used a 800 MHz FSB, was clocked at 3 GHz, and had Hyper-Threading Technology (which is what the HT moniker represents). This was meant to help the Pentium 4 better compete with AMD's Opteron line of processors. However, when the Opteron was launched, due to its server-oriented positioning motherboard manufacturers did not initially build motherboards with AGP controllers. Because AGP was the primary graphics expansion port at the time, this missing feature prevented the Opteron from encroaching on the Pentium 4's market segment. With the launch of the Athlon XP 3200+, AMD boosted the Athlon XP's FSB speed from 333 MHz to 400 MHz, but it was not enough to hold off the new 3 GHz Pentium 4 HT. The Pentium 4 HT's bandwidth levels were well out of reach for the Athlon, which would achieve the same bandwidth if its EV6 FSB was clocked to speeds unreachable at the time. 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. When core voltage was increased past 1.7 V, the processor would slowly become more unstable over time, before dying and becoming totally unusable. This became known as Sudden Northwood Death Syndrome (SNDS), which is caused by electromigration.

Pentium 4-M

Also based on the Northwood core, the Mobile Intel Pentium 4 Processor - M was released on April 23, 2002 and included Intel's SpeedStep and Deeper Sleep technologies. Intel's naming conventions made it difficult at the time of the processor's release to identify the processor model. There was the Pentium III mobile chip, the Mobile Pentium 4-M, the Mobile Pentium 4, and then just the Pentium M which itself was based on the Pentium III and significantly faster than the former three. Its TDP is about 35 watts in most applications. This lowered power consumption was due to lowered core voltage, and other features mentioned previously.

Unlike the desktop Pentium 4, the Pentium 4-M did not feature an integrated heat spreader (IHS) as the voltage is lowered. The lower voltage also means a lower resistance, and in turn less heat is produced. However, according to Intel specifications, the Pentium 4-M had a thermal junction temperature of 100 degrees, in other words, about 40 degrees more than the desktop Pentium 4. This is due to the fact that it does not have an IHS but at the same time, the majority of cooling systems were capable of running the CPU at far lower temperatures.

Mobile Pentium 4

The Mobile Intel Pentium 4 Processor 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 MHz FSB, following the desktop Pentium 4's evolution. Oddly, increasing the bus speed by 133 MHz (33 MHz core) caused a massive increase in TDPs, as mobile Pentium 4 processors gave off 59.8 W - 70 W of heat, with the Hyper-Threading variants giving off 66.1 W - 88 W. This allowed the mobile Pentium 4 to bridge the gap between the desktop Pentium 4 (giving off 115 W maximum), and the Pentium 4-M (giving off 35 W maximum).

Gallatin (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 MHz bus, twice as fast as that of the Xeon MP. An LGA 775 version is also available.

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 $999, it was also referred to as the "Expensive Edition" or "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 the Athlon 64 winning every single major benchmark over the existing Pentium 4s, which it would otherwise have done.

A slight performance increase was achieved in late 2004 by increasing the bus speed from 800 MHz to 1066 MHz, 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 MHz 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 instruction set.

Although never a particularly good seller, especially since it was released in a time when AMD were 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, and most recently, the Core i7.

Prescott

Top view of an Intel Pentium 4 Prescott 640 model Top view of a Pentium 4 Prescott 640, 3.2 GHz

Bottom view of an Intel Pentium 4 Prescott 640 model Bottom view of a Pentium 4 Prescott 640

On February 1, 2004, Intel introduced a new core codenamed "Prescott". The core used a 90 nm process for the first time, which one analyst described as "a major reworking of the Pentium 4's microarchitecture—major enough that I am surprised Intel did not opt to call this processor the Pentium 5." Despite this overhaul, the performance gains were inconsistent. Some programs benefited from Prescott's doubled cache and SSE3 instructions, whereas others were negatively impacted by its longer pipeline. The Prescott's microarchitecture allowed Prescott to be clocked at slightly higher rates, but not nearly as high as Intel had anticipated. (See Overclocking.) 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 ultimately scaled just 12% beyond Northwood.

The "Prescott" Pentium 4 contains 125 million transistors and has a die area of 122 mm². It was fabricated in a 90 nm process with seven levels of copper interconnect. The process has features such as strained silicon transistors and Low-K carbon-doped silicon oxide (CDO) dielectric, which is also known as organosilicate glass (OSG). The Prescott was first fabricated at the D1C development fab and was later moved to F11X production fab.

Originally, two Prescott lines were released: the E-series, with an 800 MHz FSB and Hyper-Threading support, and the low-end A-series, with a 533 MHz FSB and Hyper-Threading disabled. Intel eventually added XD Bit (eXecute Disable) and Intel 64 functionality to Prescott.

LGA 775 Prescott uses a rating system, labeling them as the 5xx series (Celeron Ds are the 3xx series, while Pentium Ms are the 7xx series). The LGA 775 version of the E-series uses model numbers 5x0 (520-560), and the LGA 775 version of the A-series uses model numbers 5x5 and 5x9 (505-519). The fastest, the 570J and 571, is clocked at 3.8 GHz. Plans to mass-produce a 4 GHz Pentium 4 were cancelled by Intel in favor of dual core processors, although some European retailers claimed to be selling a Pentium 4 580, clocked at 4 GHz.

The 5x0J series (and its low-end equivalent, the 5x5J and 5x9J series) introduced the XD Bit (eXecute Disable) or Execute Disabled Bit [1] to Intel's line of processors. This technology, introduced to the x86 line by AMD and called NX (No eXecute), can help prevent certain types of malicious code from exploiting a buffer overflow to get executed. Intel also released a series of Prescott supporting Intel 64, Intel's implementation of the x86-64 64-bit extensions to the x86 architecture. These were originally released as the F-series, and only sold to OEMs, but they were later renamed to the 5x1 series and sold to the general public. Two low-end Intel64-enabled Prescotts, based on the 5x5/5x9 series, were also released with model numbers 506 and 516. 5x0, 5x0J, and 5x1 series Prescott incorporates Hyper-Threading in order to speed up some processes that use multithreaded software, such as video editing. The 5x1 series also supports 64 bit computing.

Prescott would ultimately be the last codename within the NetBurst microarchitecture altogether. Its successor, the Pentium M, would pursue trends toward wider CPU microarchitecture and slower clock speeds would align with their process roadmap to reduce power and continue to increase performance. The little-funded Israeli design team that produced the Pentium M core took over this next microarchitecture iteration. The Pentium M was launched to address the mobile Pentium 4's and Pentium 4-M's performance and heat output issues. While it was clocked at much slower speeds when compared to the mobile Pentium 4, it was significantly faster, clock for clock. For example, a 1.6 GHz Pentium M could have approximately the same performance of a 2.4 GHz mobile Pentium 4. While it was intended for use only in laptops, a few manufacturers made desktop motherboards that used the socket that the Pentium M supported.

Prescott 2M (Extreme Edition)

Intel, by the first quarter of 2005, released a new Prescott core with 6x0 numbering, codenamed "Prescott 2M". Prescott 2M is also sometimes known by the name of its Xeon derivative, "Irwindale". It features Intel 64, the XD Bit, EIST (Enhanced Intel SpeedStep Technology), Tm2 (for processors at 3.6 GHz and above), and 2 MB of L2 cache. However, any advantage introduced by the added cache is mostly negated due to higher cache latency, and the double word size if using Intel 64 mode. Rather than being a targeted speed boost the double size cache is intended to provide the same space and hence performance for 64-bit mode operations.

6xx series Prescott 2Ms have incorporated Hyper-Threading in order to speed up some processes that use multithreaded software, such as video editing.

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 simply a straightforward die shrink of the Prescott-based 600 series core to 65 nm, with no real feature additions. Cedar Mill had a lower heat output than Prescott, with a TDP of 86 W. The Core Stepping of D0 in late 2006 reduced this to 65 watts. It has a 65 nm core and features a 31-stage pipeline (just like Prescott), 800 MHz FSB, Intel 64, Hyper-Threading and Virtualization Technology. As with Prescott 2M, Cedar Mill also has a 2 MB L2 cache. It was released as Pentium 6x1 and 6x3 (product code 80552) at frequencies from 3 GHz up to 3.6 GHz. Overclockers managed to exceed 8 GHz with these processors using liquid Nitrogen cooling. None of the 6x1 range (631, 641, 651, and 661) has Virtualization Technology support. As of March 2007, it has not been possible to obtain 6x3, nor had Intel any records of this product line on their website.

To distinguish Cedar Mill cores from Prescott cores with the same features, Intel added 1 to their model numbers. Thus, Pentium 4 631, 641, 651 and 661 are 65 nm microprocessors, while Pentium 630, 640, 650 and 660 respectively are their 90 nm equivalents.

The name "Cedar Mill" refers to Cedar Mill, Oregon, a neighborhood near Intel's Hillsboro, Oregon facilities.

Successor

Main article: Intel Core 2

The original successor to the Pentium 4 was (codenamed) Tejas, which was scheduled for an early-mid-2005 release. However, it was cancelled a few months after the release of Prescott due to extremely high TDPs (a 2.8 GHz Tejas gave off 150 W of heat, compared to around 80 W for a Northwood of the same speed, and 100 W for a comparably clocked Prescott) and development on the NetBurst microarchitecture as a whole ceased, with the exception of the dual-core Pentium D and Pentium Extreme Edition and the Cedar Mill-based Pentium 4 HT.

Since May 2005, Intel has released dual-core processors based on the Pentium 4 under the names Pentium D and Pentium Extreme Edition. They represent Intel's shift towards parallelism and their intent is eventually to make the bulk of their main processor line multiple-core. These came under the code names Smithfield and Presler for the 90 nm and 65 nm parts respectively.

The ultimate successors to Pentium 4 are the Intel Core 2 processors using the "Conroe" core based upon the Core microarchitecture, released on July 27, 2006. Intel Core 2 processors have been released as single, dual and quad core processors. Single core counterparts are present in the Intel Core 2 line, primarily for the OEM market, while dual and quad core processors can be sold to retail and OEM.

See also

• Intel Core 2
• List of Intel Pentium 4 microprocessors
• List of all Intel microprocessors

External links

• The future of Prescott: when Moore gives you lemons... at Ars Technica
• Prescott vs. Northwood Pentium 4 Review
• Intel Documentation
• Inside Pentium 4 Architecture