Pentium processors

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The Pentium brand refers to Intel's line of single-core mainstream and high-end 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 micro-architecture, called Net-Burst, which was the company's first all-new design since 1995, when the Intel P6 micro-architecture of the Pentium Pro CPUs had been introduced. Net-Burst differed from the preceding Intel 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 Prescott's 2M cores (a high TDP requires additional cooling that can be 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.

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 that of a normal bus, so it was considered to run at 400 MHz's. The AMD Athlon's FSB was running at 266 MHz (using a double-pumped bus) at that time. Pentium 4 CPUs introduced the SSE2 and, in later versions, SSE3 instruction sets to accelerate calculations, transactions, media processing, 3D graphics, and games. Later versions featured Hyper-threading (HTT), a feature to make one physical CPU work as two logical and virtual CPUs. Intel also marketed a version of their low-end

Celeron processors based on the Net-Burst micro-architecture (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

Introduction of Pentium Processor

The original Pentium processor was a 32-bit microprocessor produced by Intel. The first superscalar x86 architecture processor, it was introduced on March 22, 1993. Its micro-architecture (sometimes called P5) was a direct extension of the 80486 architecture with dual integer pipelines, a faster FPU, wider data bus, and features for further reduced address calculation latency. In 1996, the Pentium MMX was introduced with the same basic micro-architecture complemented with MMX instructions, larger caches, and some other enhancements. The name Pentium was derived from the Greek pente, meaning 'five', and the Latin ending -ium, a name selected after courts had disallowed trade marking of number-based names like "i586" or "80586". In 1995, Intel started to employ the registered Pentium trademark also for x86 processors with radically different micro-architectures (Pentium Pro / II / III / 4 / D / M). In 2006, the Pentium brand briefly disappeared from Intel's roadmaps, only to re-emerge in 2007.

Block diagram of the Pentium

Pentium Processor-1

The original Pentium processor was a 32-bit microprocessor produced by Intel. The first superscalar x86 architecture processor, it was introduced on March 22, 1993. Its micro-architecture (sometimes called P5) was a direct extension of the 80486 architecture with dual integer pipelines, a faster FPU, wider data bus, and features for further reduced address calculation latency. In 1996, the Pentium MMX was introduced with the same basic micro-architecture complemented with MMX instructions, larger caches, and some other enhancements. The name Pentium was derived from the Greek pente, meaning 'five', and the Latin ending -ium.

Architecture of Pentium 1

It had two five-stage integer pipelines, which Intel designated U and V, and one six-stage floating-point pipeline. The chip's front-end could do dynamic branch prediction, but as we'll learn in a moment most of its front-end resources were spent on maintaining backwards compatibility with the x86 architecture.

The Pentium's U and V integer pipes were not fully symmetric. U, as the default pipe, was slightly more capable and contained a shifter, which V lacked. The two pipelines weren't fully independent, either; there was a set of restrictions, which I won't waste anyone's time outlining, that placed limits on which combinations of integer instructions could be issued in parallel. All told, though, the Pentium's two integer pipes provided solid enough integer performance to be competitive, especially for integer-intensive office apps.

Floating-point, however, simply went from awful on the 486 to just mediocre with the Pentium ? an improvement, to be sure, but not enough to make it even remotely competitive with comparable RISC chips on the market at that time. First off, you could only issue both a floating-point and an integer operation simultaneously under extremely restrictive circumstances. This wasn't too bad, because floating-point and integer code are rarely mixed. The killer, though, was the unfortunate design of the x87 stack-based floating-point architecture.


Introduction date: March 22, 1993

Process: 0.8 micron

Transistor Count: 3.1 million

Clock speed 60 and 66 MHz

Cache sizes: L1: 8K instruction

Features: MMX added in 1997


The Pentium II microprocessor was largely based upon the micro architecture of its predecessor, the Pentium Pro, but with some significant improvements. Unlike previous Pentium and Pentium Pro processors, the Pentium II CPU was packaged in a slot-based module rather than a CPU socket. The processor and associated components were carried on a daughterboard similar to a typical expansion board within a plastic cartridge. A fixed or removable heat sink was carried on one side, sometimes using its own fan.[2]

The Pentium II brand refers to Intel's sixth-generation micro architecture ("Intel P6") and x86-compatible microprocessors introduced on May 7, 1997. Containing 7.5 million transistors, the Pentium II featured an improved version of the first P6-generation core of the Pentium Pro, which contained 5.5 million transistors. However, its L2 cache subsystem was a downgrade when compared to Pentium Pro's. In early 1999, the Pentium II was superseded by the Pentium III. In 1998, Intel stratified the Pentium II family by releasing the Pentium II-based Celeron line of processors for low-end workstations and the Pentium II Xeon line for servers and high-end workstations. The Celeron was characterized by a reduced or omitted (in some cases present but disabled) on-die full-speed L2 cache and a 66 MT/s FSB.


Produced From mid 1997 to early 1999

Common manufacturer(s) Intel

Max. CPU clock rate 233MHz to 450MHz

FSB speeds 66MHz to 100MHz

Min. feature size 0.35µm to 0.25µm

Instruction set x86, MMX

Microarchitecture P6

Cores 1

Socket(s) Slot 1




Core name(s) Deschutes


Pentium-1 Vs Pentium-2

The first Pentium processor was introduced that ran at a clock speed of 60 and 66 MHz whereas the Pentium 2 was introduced when the first Pentium processor technology became obsolete. It was designed to run from 233 MHz to 450 MHz.

Front Side Bus (FSB) speed has a dramatic effect on the overall performance of a computer system. Front Side Bus (FSB) speed of Pentium -1 is 50-60 MHz whereas FSB speed of Pentium-2 is 66MHz -100MHz.


The Pentium III brand refers to Intel's 32-bit x86 desktop and mobile microprocessors based on the sixth-generation Intel P6 micro architecture introduced on February 26, 1999. The brand's initial processors were very similar to the earlier Pentium II-branded microprocessors. The most notable difference was the addition of the SSE instruction set (to accelerate floating point and parallel calculations),

Similarly to the Pentium II it superseded, the Pentium III was also accompanied by the Celeron brand for lower-end versions, and the Xeon for high-end (server and workstation) derivatives. The Pentium III was eventually superseded by the Pentium 4, but its Tualatin core also served as the basis for the Pentium M CPUs, which used many ideas from the Intel P6 micro architecture. Subsequently, it was the P-M micro architecture of Pentium M branded CPUs, and not the NetBurst found in Pentium 4 processors, that formed the basis for Intel's energy-efficient Intel Core micro architecture of CPUs branded Core 2, Pentium Dual-Core, Celeron (Core), and Xeon.

Architecture of Pentium -3

The Pentium III processor is the first implementation of the Internet SSE. The Internet SSE contains 70 new instructions and a new architectural state. It is the second significant extension of the instruction set since the 80386 and the first to add a new architectural state. MMXÔ was the first significant instruction extension, but it did not add any new architectural state. The new instructions fall into different categories:

Ø SIMD FP instructions that operate on four single precision numbers

Ø Scalar FP instructions

Ø Cache ability instructions including prefetches into different levels of the cache hierarchy

Ø control instructions

Ø data conversion instructions


  • 1.26 GHz 370-pin FC-PGA2 package with 512 KB Advanced Transfer Cache (on-die, full-speed L2 cache)
  • 1 GHz, 866, 850, 733, 700 and 600 MHz, 370-pin FC-PGA package
  • 700, 500 and 400 MHz BGA2 package
  • 1 GHz, 866 and 733 MHz processor supports 133 MHz processor side bus
  • 256 Kbytes Advanced Transfer Cache (on-die, full-speed L2 cache)
  • Compatible with Intel® 840, 815, 815E, 810E2, 810 chipsets; Intel® 82801E C-ICH; Intel® 440BX AGPset and 440MX chipset

Intel Pentium III processor family




Date released









May 1999

Mar 2000

Aug 2000

Apr 2001

List of Intel Pentium III microprocessors

Pentium-2 Vs Pentium-3

  • The Pentium-2 was designed to run from 233 MHz to 450 MHz whereas Pentium-3 was processor replaced the Pentium 2 and ran at a clock speed of 450 MHz to 1.4 GHz.
  • Front Side Bus (FSB) speed has a dramatic effect on the overall performance of a computer system. Front Side Bus (FSB) speed of Pentium-2 is 66MHz -100MHz speed of Pentium -3 is 100MHz to 133MHz


The Pentium 4 family of processors, which has its roots in the Intel486(TM) processor, uses the Intel486 instruction set (with a few additional instructions). The term ''Pentium processor'' refers to a family of microprocessors that share a common architecture and instruction set. The first Pentium processors (the P5 variety) were introduced in 1993. This 5.0-V processor was fabricated in 0.8-micron bipolar complementary metal oxide semiconductor (BiCMOS) technology. The P5 processor runs at a clock frequency of either 60 or 66 MHz and has 3.1 million transistors.

The Intel Pentium processor, like its predecessor the Intel486 microprocessor, is fully software compatible with the installed base of over 100 million compatible Intel architecture systems. In addition, the Intel Pentium processor provides new levels of performance to new and existing software through a reimplementation of the Intel 32-bit instruction set architecture using the latest, most advanced, design techniques. Optimized, dual execution units provide one-clock execution for "core" instructions, while advanced technology, such as superscalar architecture, branch prediction, and execution pipelining, enables multiple instructions to execute in parallel with high efficiency. Separate code and data caches combined with wide 128-bit and 256-bit internal data paths and a 64-bit, burstable, external bus allow these performance levels to be sustained in cost-effective systems. The application of this advanced technology in the Intel Pentium processor brings "state of the art" performance and capability to existing Intel architecture software as well as new and advanced applications.


Clock Speed: 1.3 - 3.06GHz

FSB Speed: 400 - 800MHz

L1 Cache: 8 KB

L2 Cache: 256 - 512 MB

Introduction: 2000

Package: PGA

Socket: Socket 423 and Socket 478

Operating Modes

The Pentium processor has two primary operating modes which are discussed below and a "system management mode." The operating mode determines which instructions and architectural features are accessible. These modes are:

Protected Mode

Real-Address Mode (also called "real mode")

System Management Mode

Protected Mode

This is the native state of the microprocessor. In this mode, all instructions and architectural features are available, providing the highest performance and capability. This is the recommended mode that all new applications and operating systems should target. Among the capabilities of protected mode is the ability to directly execute "real-address mode" 8086 software in a protected, multi-tasking environment. This feature is known as Virtual-8086 "mode" (or "V86 mode").

Real-Address Mode (also called "Real Mode")

This mode provides the programming environment of the Intel 8086 processor, with a few extensions (such as the ability to break out of this mode). Reset initialization places the processor in real mode where, with a single instruction, it can switch to protected mode.

System Management Mode

The Pentium microprocessor also provides support for System Management Mode (SMM). SMM is a standard architectural feature unique to all new Intel microprocessors, beginning with the Intel386 SL processor, which provides an operating-system and application independent and transparent mechanism to implement system power management and OEM differentiation features. SMM is entered through activation of an external interrupt pin (SMI#), which switches the CPU to a separate address space while saving the entire context of the CPU. SMM-specific code may then be executed transparently. The operation is reversed upon returning.

Architecture of Pentium 4

With a 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 unit-directional bus. Furthermore, the Net Burst micro architecture gave off more heat than any previous Intel or AMD microarchitecures.

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 (reaching a peak clock speed of 1.4 GHz) 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 Net Burst micro architecture was often referred to as an architecture by various computing websites and publications during the life of the Pentium 4.

At the launch of the Pentium 4, Intel stated Net Burst-based processors were expected to scale to 10 GHz (which should be achieved over several fabrication process generations). However, the Net Burst micro architecture ultimately hit a frequency ceiling far below that expectation — the fastest clocked Pentium 4 models reached a peak clock speed of 3.8 GHz and a maximum TDP of 115 W. 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, such as using multiple cores, increasing FSB speeds, increasing the cache size, and using a shorter, more efficient pipeline along with lower clock speeds.

Pentium-3 Vs Pentium-4

  • The Pentium-3 was designed to run from 450 MHz to 1.4 GHz whereas Pentium-4 has processor replaced the Pentium-3 and ran at a clock speed of 1.3 GHz to 3.8 GHz.
  • Front Side Bus (FSB) speed has a dramatic effect on the overall performance of a computer system. Front Side Bus (FSB) speed of Pentium-3 is 100MHz -133MHz speed of Pentium-4 is 400 MT/s to 1066 MT/s

Today's Processor: - AMD Athlon XP

AMD introduced their new line of Athlon processor: the Athlon XP. While still an Athlon processor, the Athlon XP does not use the conventional MHz rating to depict its speed.AMD believes that a MHz rating would undermine its true performance and therefore wishes to change public perception. For those who insist of raw MHz numbers, AMD claims a 25% performance increase of their XP 1900+ compared to a Pentium 4 running at 1900 MHz.

AMD Athlon XP speed rating calculation

MHz = (XP rating/1.5) + (500/1.5)

For example, using the 1800+ processor

MHz = (1800+/1.5) + (500/1.5)

MHz = 1200 + ~333.33333333...

MHz = ~1533.33

The sign ~ means "approximately." Since .333 is infinitely repeated, it's just nice way to represent "short form.

Microprocessor Comparison Chart

Transistors CPU Speed L2 Cache Front-Side Bus Speed

Celeron 7,500,000 1.06 GHz - 2 GHz 256 KB, full speed 133MHz- 400 MHz

Pentium II 7,500,000 233 MHz - 450MHz 512 KB, half speed 100 MHz

Pentium III 9,500,000 450 MHz - 1 GHz 256 KB, full speed 133 MHz

P- III Xeon 28,100,000 500 MHz - 1 GHz 256KB-2 MB, full 100 MHz

Pentium- 4 55,000,000 1.4 GHz - 3.4 GHz 256 KB, full speed 800 MHz

K6-II 9,300,000 500 MHz - 550 MHz N/A 100 MHz

K6-III 21,300,000 400 MHz - 450 MHz 256 KB, full speed 100 MHz

Athlon (K7) 22,000,000 850 MHz - 1.2 GHz 256 KB, full speed 200 MHz- 266 MHz

Athlon XP 37,500,000 1.67 GHz 384 KB, full speed 266 MHz

Duron N/A 700-800 MHz 64 KB, full speed 200 MHz

PowerPC G3 6,500,000 233 MHz - 333 MHz 1 MB, half speed 100 MHz

PowerPC G4 10,500,000 400 MHz - 800 MHz 1 MB, half speed 100 MHz

Athlon 64 105,900,000 800 MHz 1 MB, half speed 1.6 GHz

G5 58,000,000 2.5GHz 512 KB 900MHz - 1.25GHz