Pentium 4
From Wikipedia, the free encyclopedia
| Pentium 4 Central processing unit |
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 An LGA 775 Pentium 4 |
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| Produced: | 2000- |
| Manufacturer: | Intel |
| CPU Speeds: | 1.3 GHz to 3.8 GHz |
| FSB Speeds: | 400 MT/s to 1066 MT/s |
| Process: (MOSFET channel length) |
0.18 µm to 0.065 µm |
| Instruction Set: | x86 (i386), x86-64 |
| Microarchitecture: | NetBurst |
| Sockets: | |
Cores:
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The Pentium 4 is a seventh-generation x86 architecture microprocessor produced by Intel and was the company's first all-new CPU design since the Pentium Pro of 1995. Unlike the Pentium II, Pentium III, and various Celerons, the architecture owed little to the Intel P6 design. The "NetBurst" microarchitecture featured a very deep instruction pipeline, with the intention of scaling to very high frequencies. It also introduced the SSE2 SIMD instruction set for faster integer and 64-bit floating-point computation. Later Pentium 4 models integrated technological advances such as Hyper-threading, a feature to make one physical CPU appear as two logical and virtual CPUs.
The original Pentium 4, codenamed "Willamette", launched with models at 1.4 and 1.5 GHz and was released in November 2000 on the Socket 423 platform, and later Socket 478 from 1.5 GHz to 2.0 GHz. Notable with the introduction of the Pentium 4 was the comparatively fast 400 MT/s FSB. It was actually based on a 100 MHz clock wave, but the bus was quad-pumped, meaning that the maximum transfer rate was four times that of a normal bus, so it was considered to run at 400 MT/s.
As is traditional with Intel's flagship chips, the Pentium 4 also came in a low-end Celeron version (often referred to as Celeron 4) and a high-end Xeon version intended for SMP configurations. Nearly 6 years after the introduction of the original Pentium 4 CPUs, a dual core version, called the Pentium D, was released.
The Pentium 4 line of processors was retired on July 27, 2006, replaced by the Intel Core 2 line, using the "Conroe" core.
Contents |
[edit] Architecture
In benchmark evaluations, the advantages of the NetBurst architecture were not clear. With carefully optimized application code, the first P4 did outperform Intel's fastest Pentium III, as expected. But in legacy applications with many branching or x87 floating-point instructions, the P4 would merely match or even fall behind its predecessor. Furthermore, the NetBurst architecture dissipated more heat than any previous Intel or AMD processor.
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 much lower-clocked Athlon easily outperformed the Pentium 4, which would only catch up if software were re-compiled with SSE2 support. 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 architecture 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-frequency. While IPC is difficult to quantify (due to dependence on the benchmark application's instruction mix), clock-frequency is a simple measurement yielding a single absolute number. Unsophisticated buyers would simply associate the highest clock-rating with 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
At the launch of the P4, Intel stated NetBurst was expected to scale to 10 GHz (over several fabrication process generations). However, the NetBurst architecture ultimately hit a frequency ceiling far below expectation—the fastest retail Pentium 4 never exceeded 4 GHz. Intel had not anticipated a rapid upward scaling of transistor power leakage that began to occur as the chip reached the 90 nm process node 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. Nothing solved their problems though and in 2005-6 Intel shifted development away from NetBurst to focus on the cooler running Pentium M architecture. In March 2006, Intel announced the Intel Core microarchitecture, which puts greater emphasis on energy efficiency and performance per clock. The final NetBurst-derived products were released in 2006, with all subsequent product families switching exclusively to the Intel Core microarchitecture.
[edit] Processor cores
The Pentium 4 has an IHS (Integrated Heat Spreader) that prevents 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 Willamette and Northwood cores to allow for more direct heat transfer. However, in revisions since Prescott the IHS is directly welded to the processor core, meaning that the IHS cannot be removed without irreparably damaging the chip.
[edit] Willamette
Willamette, the first Pentium 4, suffered long delays in the design process. The project was originally started in 1998, when Intel saw the Pentium II as their permanent line. At that time, the Willamette core was only expected to operate at frequencies of around 1 GHz. However, development delays saw the introduction of the Pentium III and the radical differences in these architectures meant Intel could not market Willamette as a Pentium III. Thus, it was named Pentium 4, ending Intel's Roman-numeral nomenclature system.
In November 2000, Intel released the Willamette Pentium 4 at speeds of 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 Willamette was released because the competing AMD Athlon Thunderbird was at that time outperforming the elderly Pentium III, and further improvements to the P-III were not yet possible. The cores were produced using a 0.18 micrometer (180 nm) process and initially utilized Socket 423 on motherboards, 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 clearly not superior to even the low-end 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 1.3 GHz model was added to the range, but over the next twelve months, Intel gradually started pegging back AMD's lead. April 2001 brought the 1.7 GHz P4, the first one 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 2.0 GHz Pentium 4s. In the same month, they released a new chipset that supported much cheaper PC133 SDRAM. While use of this RAM was much slower than RDRAM, the fact that PC133 was much cheaper caused the Pentium 4's sales to massively improve, displacing the Pentium III virtually overnight to become the top-selling processor on the market.
The 2.0 GHz was the first P4 to provide a serious challenge to the rival Athlon Thunderbird, which until then had been unquestionably the fastest x86 CPU on the market. Many observers concluded that the Thunderbird was still faster overall, but the performance gap was sufficiently narrow that it was not unreasonable for partisans of either camp to claim superiority. For Intel, this was a very significant achievement. The firm had held the x86 CPU performance crown for nearly 16 years straight, with only two brief exceptions prior to the release of the AMD Athlon.
The Willamette code name is derived from the Willamette River and Willamette Valley region of Oregon, where a large number of Intel manufacturing facilities are located.
[edit] Northwood
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, 1.8, 2.0 and 2.2 GHz. Northwood (product code 80532) combined an increase in the secondary cache size from 256 KiB to 512 KiB (increasing the transistor count to 55 million, up from 42 million) with a transition to a new 130 nm (0.13 micrometer) fabrication process. By making the chip out of smaller transistors, chips can run at higher clocks or at the same speed while producing less heat. Unfortunately for many consumers, the new core also made upgrades impossible due to the requirement of a new socket (Socket 478), although later adapters were made for Socket 423 to utilize the Northwood processors.
With Northwood, the P4 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 Northwood P4 was usually a fraction ahead of its rival.[citation needed] This was particularly so in the summer of 2002, when AMD's changeover to a 130 nm production process was delayed and the P4s in the 2.4 to 2.8 GHz range were clearly the fastest chips on the market.
A 2.4 GHz P4 was released in April 2002, and the bus speed increased from 400 MT/s to 533 MT/s for a 2.26 GHz, 2.4 GHz, and 2.53 GHz part in May, 2.6 and 2.8 GHz parts in August, and a 3.06 GHz Pentium 4 arrived in November.
The 3.06 GHz processor supported Hyper-Threading (first appeared in Xeon), enabling multiple threads to be run together by duplicating some parts of the processor in order to let the operating system believe that there are two logical processors. HyperThreading was present in all Northwood CPUs, but was disabled in the core in all but the 3.06 GHz model.
In April 2003, Intel launched new 800 MT/s FSB variants, ranging from 2.4 to 3.0 GHz. The key difference on these new versions was that they all supported Hyper-Threading, and ran their system buses at 800 MT/s. This was supposedly to compete better with AMD's Hammer line of processors. However, only Opteron was launched, and motherboard manufactures initially refused to build Opteron-based motherboards with an AGP controller, thus preventing the Opteron from encroaching on the Pentium 4's territory. AMD did boost the Athlon XP's bus speed from 333 MT/s to 400 MT/s, but it wasn't enough to hold off the new 3.0 GHz P4– and the FSB wasn't the problem; the 333 MT/s to 400 MT/s transition yielded little to no performance increase. A 3.2 GHz variant was launched in June and a final 3.4 GHz version was launched in early 2004.
Overclocking early stepping Northwood cores yielded a startling phenomenon. When VCore was increased past 1.7 V, the processor would slowly become more unstable over time, before dying and becoming totally unusable. This is believed to have been caused by the physical phenomenon known as Electromigration, where the internal pathways of the CPU become degraded over time due to excessive electron energy. This was also known as Sudden Northwood Death Syndrome.
[edit] Mobile Pentium 4
The Mobile Intel Pentium 4 Processor [1] was released to address the problem of putting a full Pentium 4 desktop chip into a laptop, which some manufacturers were doing. The Mobile P4 still used 70 W of power, which let it bridge the gap between the full Pentium 4 (using about 82 W), and the Mobile Pentium 4 M (using about 35 W).
[edit] Mobile Pentium 4 M
Also based on the Northwood core, the Mobile Intel Pentium 4 Processor - M [2] was released on April 23, 2002 [3] and included Intel's SpeedStep and Deeper Sleep technologies, but not Hyper-Threading. 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 (or the PIII-M), the Mobile Pentium 4 M (or the P4-M), the Mobile Pentium 4 (or the Mobile P4), and then just the Pentium M which itself was based on the Pentium III.
[edit] 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 (AMD64 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 MiB 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. An LGA 775 version is also available.
While Intel maintained that the Extreme Edition was aimed at gamers, some viewed it as an attempt to steal the Athlon 64's launch thunder, nicknaming it the "Emergency Edition". Many condemned Intel for cannibalizing the Xeon line, but because of this, no such complaints were aimed at AMD, who retaliated by doing the same with their Athlon 64 FX.
The effect of the added cache was somewhat variable. In office applications, the Extreme Edition was generally a bit slower than the Northwood, owing to higher latency added by the L3 cache. Some games benefited from the added cache, particularly those based on the Quake III and Unreal engines. However, the area which improved the most was multimedia encoding, which was not only faster than the Pentium 4, but also both Athlon 64s.
A slight performance increase was achieved in late 2004 by increasing the bus speed from 800 MT/s to 1066 MT/s. Only one Gallatin-based chip at 3.46 GHz was released before the 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 Extreme Edition almost always proved to be slower than the 3.46 GHz version.
The 'Pentium 4 Extreme Edition' should not be confused with a similarly-named later model, the 'Pentium Extreme Edition', which is based on the dual-core Pentium D.
[edit] Prescott
On February 1, 2004, Intel introduced a new core codenamed "Prescott." The core uses a 90 nm process for the first time, and "[it] is also a major reworking of the Pentium 4's microarchitecture - major enough that some analysts are surprised Intel didn't opt to call this processor the Pentium 5" ([4]). Although a Prescott clocked at the same rate as a Northwood, benchmarks show that a Northwood runs slightly faster than a Prescott in gaming applications. However, with video editing and other multimedia software, the Prescott's extra cache and SSE3 instructions give it a clear speed advantage over the Northwood. The Prescott architecture allows it to be easily set at higher clock-rates. (See Overclocking.) 3.8 GHz was the fastest Prescott-based processor ever mass-produced.
Upon release, the Prescott turned out to generate approximately 40% more heat clock-for-clock than the Northwood, and almost every review of it was negative, earning it the soubriquet PresHot. A shift in socket type (from Socket 478 to LGA775) was expected to reduce the heat to more acceptable levels, but in fact proved to have the opposite effect, with power requirements increasing by a further 10%. However, the LGA775 reference cooler and mounting system were somewhat better designs, so average temperatures were slightly lowered. Subsequent revisions to the processor by Intel engineers were expected to reduce average temperatures, but this never happened outside of the lowest speed grades. Prescott Pentium 4s were given the product codes 80546 (Socket 478) and 80547 (LGA775).
Finally, the thermal problems were so severe, Intel decided to abandon the Prescott architecture altogether, and attempts to roll out a 4 GHz part were abandoned, as a waste of internal resources. Also of concern was the fact that a review showed that in games, it took a 5.2 GHz Prescott core to soundly beat the performance of an Athlon FX-55 that clocked at 2.6 GHz [5]. Considering Intel boasted at launch the Pentium 4 architecture was intended to support up to 10 GHz operation, this can be seen as one of the most significant, certainly most public, engineering shortfalls in Intel’s history. This also meant that while Northwood ultimately achieved clockspeeds 70% higher than Willamette did, Prescott only managed a 12% rise over Northwood.
The Pentium M instead became the internal reference layout for Intel’s design teams, and P4 development was essentially abandoned. To this extent, the little-funded Israeli design team that produced the Pentium M core took over the much larger desktop development project.
Why the Prescott ended up in such a disaster can be attributed to internal politics at Intel as much as to poor design. The engineering group was not able to meet the marketing departments desire for ever higher clock speeds, to differentiate their products from AMD. The processor design was not able to clock at the higher speeds required for increased performance and the power consumption was simply untenable. The engineering group kept this information from people in other departments at Intel until it was too late. The termination of the P4 project, when it finally came, had consequences for many members of the management team at the well-funded desktop division, but unfortunately, not so much in the engineering or manufacturing groups.
Originally, two Prescott lines were released: the E-series, with an 800 MT/s FSB and Hyper-Threading support, and the low-end A-series, with a 533 MT/s FSB and Hyper-Threading disabled. Initially there were big problems with people who installed Windows XP Service Pack 2 on systems with these processors as an incompatibility with the BIOS, processor and SP2 coding led to systems unable to boot. Microsoft and Intel worked on a solution; Users with this problem can find out how to install SP2 on a Prescott machine.
LGA775 Prescotts use a rating system, labeling them as the 5xx series (Celerons are the 3xx series, while Pentium Ms are the 7xx series). The LGA775 version of the E-series uses model numbers 5x0 (520-560), and the LGA775 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 for 4 GHz processors were axed by Intel in favor of dual core processors, although some European retailers claim 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 [6] to Intel's line of processors. This technology, first 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 Prescotts supporting Intel 64, Intel's implementation of the AMD64 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 Prescotts have incorporated Hyper-Threading in order to speed up some processes that use multithreaded software, such as video editing. This CPU also supports 64 bit computing.
[edit] Prescott 2M
Intel, by the first quarter of 2005, released a new Prescott core with 6x0 numbering, codenamed "Prescott 2M". It features Intel 64, the XD Bit, EIST (Enhanced Intel SpeedStep Technology), Tm2 (for processors at 3.6GHz and above), and 2 MiB 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 14 November 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 and 3.8 GHz, respectively.
[edit] Cedar Mill
The final revision of the Pentium 4 was Cedar Mill, released in early 2006. This was simply a straight shrink of the 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. It has a 65 nm core and features a 31-stage pipeline (just like Prescott), 800 MT/s FSB, Intel 64, HyperThreading and Virtualization Technology. As with Prescott 2M, Cedar Mill also has 2 MiB of L2 cache. It was released as Pentium 6x1 and 6x3 (product code 80552) at frequencies from 3.0 GHz up to 3.6 GHz. None of the 6x1 range (631, 641, 651, and 661) have Virtualization Technology support. As of March 2007 it has not been possible to source 6x3 nor has Intel any records of this product line on their homepage.
[edit] Successor
The original successor to the Pentium 4 was 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 power consumption (a 2.8 GHz Tejas consumed 150 W of power, 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 architecture as a whole ceased, with the exception of the dual-core Pentium D/Extreme Edition and Cedar Mill.
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 to eventually make the bulk of their main processor line dual-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 Intel Core microarchitecture, released on July 27, 2006. Intel Core 2 processors have, so far, only been released as dual and quad core processors. Single Core counterparts are present in the Intel Core line, primarily for the OEM market.
[edit] External links
- The future of Prescott: when Moore gives you lemons... at Ars Technica
- Prescott vs. Northwood Pentium 4 Review
- Intel Pentium4 technical specifications
- Brief History of the Pentium 4
- Intel Documentation
- Inside Pentium 4 Architecture
[edit] See also
| Intel processors (italics indicate non-x86 processors)
4004 | 4040 | 8008 | 8080 | 8085 | 8086 | 8088 | iAPX 432 | 80186 | 80188 | 80286 | 80386 | 80486 | i860 | i960 | Pentium | Pentium Pro | Pentium II | Celeron | Pentium III | XScale | Pentium 4 | Pentium M | Pentium D | Pentium Extreme Edition | Pentium Dual Core | Pentium E | Xeon | Core | Core 2 | Itanium | Itanium 2 List of Intel microprocessors | List of Intel CPU slots and sockets |
