Pentium (original)

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Pentium
75 MHz classic Pentium Processor
General information
Launched1993
Discontinued1999
Common manufacturer
  • Intel
Performance
Max. CPU clock rate60 MHz to 300 MHz
FSB speeds50  to 66 
Architecture and classification
Technology node0.8 to 0.25
MicroarchitectureP5
Instruction setx86
Physical specifications
Sockets
  • Socket 4
  • Socket 5
  • Socket 7
Products, models, variants
Core names
  • P5
  • P54
  • P54CS
  • P55C
  • Tillamook
This article is about the microprocessor. For the hydrogen isotope, see Hydrogen-5.

The Pentium brand name initially referred only to the fifth-generation microarchitecture of microprocessors from Intel, called Intel P5 and described here, but latter it covered also subsequent generations. So, the Pentium as Intel P5, considered here, was a successor to the 486 line, and was first shipped on March 22, 1993.

The Pentium was expected to be named 80586 or i586, to follow the naming convention of previous generations. However, Intel was unable to persuade a court to allow them to trademark a number (such as 486), in order to prevent competitors such as Advanced Micro Devices from branding their processors with similar names (such as AMD's Am486).

Intel enlisted the help of Lexicon Branding to create a brand that could be trademarked. The Pentium brand was very successful, and was and still is maintained through several generations of processors, from the Pentium Pro to the Pentium Extreme Edition and further. Although not used for marketing purposes, Pentium series processors are still given numerical product codes, starting with 80500 for the original Pentium chip.

Intel has now largely retired the Pentium brand and replaced it with the "Intel Core" brand, although it is still used on a line of value processors called Pentium Dual-Core[1]. The first Intel Core, released in January 2006, extended the Pentium M microarchitecture. The Intel Core 2, released in July 2006, features the new Intel Core microarchitecture.

Pentium logo, with MMX enhancement

Microsoft and many other companies use the original Pentium as a standard for specifications of requirements. For example, Microsoft's stated requirements for the Microsoft Visual Studio 2005 Team Edition, include (at least) a Pentium processor running at a clock speed of 600 MHz (required), or 1 GHz (recommended). To find out if another processor meets the requirement, a conversion must be used that gives its speed in terms of standard Pentium clock rates. For example, a Pentium Pro would meet the requirement running at a much lower clock speed, because of its more advanced architecture. An equivalency chart is usually used to compare more modern processors to find out if they meet this requirement.

In programming, it is sometimes necessary to distinguish the original Pentium processor architecture from later (P6 or P68-based) Pentium-branded architectures. For these cases, i586 is a common, though spurious, way to refer to the early Pentium processors, as well as processors made by Intel's competitors that can run machine code targeted to the early Pentiums.

Major changes from the 486

File:Podp5v83.jpg
Pentium Overdrive for 486 systems
  • Superscalar architecture - The Pentium has two datapaths (pipelines) that allow it to complete more than one instruction per clock cycle. One pipe (called "U") can handle any instruction, while the other (called "V") can handle the simplest, most common instructions. The use of more than one pipeline is a characteristic typical of RISC processors designs, the first of many to be implemented on the x86 platform, thus signaling the road to take, and showing that it was possible to merge both technologies, creating almost “hybrid” processors.
  • 64-bit data path - This doubles the amount of information pulled from the memory on each fetch. This doesn't mean that the Pentium can execute 64-bit applications; its main registers are still 32 bits wide.
  • MMX instructions (later models only) - A basic SIMD instruction set extension designed for use in multimedia applications.


Pentium architecture chips offered just under twice the performance of a 486 processor per clock cycle. The fastest Intel 486 parts were almost the same speed as a first-generation Pentium, and the AMD Am5x86 was roughly equal to the Pentium 75.

Models

The earliest Pentiums were released at the clock speeds of 66 MHz and 60 MHz. Later on 75, 90, 100, 120, 133, 150, 166, 200, and 233 MHz versions gradually became available. 266 and 300 MHz versions were later released for mobile computing. Pentium OverDrive processors were released at speeds of 63 and 83 MHz as an upgrade option for older 486-class computers.

Code name P5 P54C P54CS P55C Tillamook
Product code 80500/80501 80502 80503
Process size (µm) 0.80 0.60 0.35 0.28 0.25
Clock speed (MHz) 60 66 75 90 100 120 133 150 166 200 120* 133* 150* 166 200 233 200 233 266 300
Bus speed (MHz) 60 66 50 60 66 60 66 60 66 60 66 60 66
Voltage 5.0 5.0 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 2.8 2.8 2.8 2.8 2.8 2.8 1.8 1.8 1.8 1.8
Introduced 22 March 1993 10 October 1994 7 March 1994 27 March 1995 June 1995 4 January 1996 10 June 1996 27 March 1995 - 1 November 1995 8 January 1997 2 June 1997 August 1997 January 1998 January 1999
  • * These were only available as Mobile Pentium MMX chips for laptops.

P5, P54C, P54CS

The original Pentium microprocessor had the internal code name P5 and the product code 80501 (80500 for the earliest steppings). This was a pipelined in-order superscalar microprocessor, produced using a 0.8 µm process. It was followed by the P54C (80502), a shrink of the P5 to a 0.6 µm process, which was dual-processor ready and had an internal clock speed different from the front side bus (it's much more difficult to increase the bus speed than to increase the internal clock). In turn, the P54C was followed by the P54CS, which used a 0.35 µm process - a pure CMOS process, as opposed to the Bipolar CMOS process that was used for the earlier Pentiums.

The early versions of 60-100 MHz Pentiums had a problem in the floating point unit that, in rare cases, resulted in reduced precision of division operations. This bug, discovered in Lynchburg, Virginia in 1994, became known as the Pentium FDIV bug and caused great embarrassment for Intel, which created an exchange program to replace the faulty processors with corrected ones. The 60 and 66 MHz 0.8 µm versions of the Pentium processors were also known for their fragility and their (for the time) high levels of heat production - in fact, the Pentium 60 and 66 were often nicknamed "coffee warmers". They were also known as "high voltage Pentiums", due to their 5 V operation. The heat problems were removed with the P54C, which ran at a much lower voltage (3.3 V). P5 Pentiums used Socket 4, while P54C started out on Socket 5 before moving to Socket 7 in later revisions. All desktop Pentiums from P54CS onwards used Socket 7. Another bug known as f00f bug was discovered soon afterwards, but fortunately, operating system vendors responded by implementing workarounds that prevented the crash.

The 32-bit bus Pentium -- a sort of oddity among the other Pentium processors, P24T Pentium OverDrive for 486 systems were released in 1995, which were based on the 3.3 volt 0.6 µm technology at 63 or 83Mhz clock speed. Since the chips used Socket 2 or Socket 3 of the 486 platform, the Pentium architecture had to be modified in many ways to operate on narrower 32-bit data bus and slower on-board L2 cache architecture. As such, they came equipped with a 32 KiB L1 cache, double what a pre-P55C Pentium came equipped with. The chips also included an attached fan/heatsink assembly in addition to onboard power regulation to convert the 5 V power circuitry on 486 boards down to the Pentium's 3.3 V needs.

P55C, Tillamook

Pentium MMX 233 MHz (P55C, 80503) top
Pentium MMX 166 MHz without cover

The P55C (or 80503) was developed by Intel's Research & Development Center in Haifa, Israel. It was sold as Pentium with MMX Technology (usually just called Pentium MMX); although it was based on the P5 core (the 0.35 µm process was also used for this series) it featured a new set of 57 "MMX" instructions intended to improve performance on multimedia tasks, such as encoding and decoding digital media data.

The new instructions work on new data types: 64-bit packed vectors of either eight 8-bit integers, four 16-bit integers, two 32-bit integers, or one 64-bit integer. So, for example, the PADDUSB (Packed ADD Unsigned Saturated Byte) instruction adds two vectors, each containing eight 8-bit unsigned integers together, pairwise; each addition that would overflow saturates, yielding 255, the maximum unsigned value that can be represented in a byte. These rather specialized instructions generally require special coding by the programmer for them to be used. MMX did not achieve significant popularity until after the P55C's lifetime [citation needed].

The performance of the P55C was improved over previous versions by a doubling of the Level 1 CPU cache from 16 KiB to 32 KiB.

Pentium P55C notebook CPUs used a "mobile module" that held the CPU. This module was a PCB with the CPU directly attached to it in a special smaller form factor. The module snapped to the notebook motherboard and typically a heat spreader plate was installed and made contact with the module. Such notebooks frequently used the Intel 430MX chipset, a feature-reduced 430FX. However, with the 0.25 µm Tillamook Mobile Pentium MMX (named after a city in Oregon), the module also held the 430TX chipset along with the system's 512 KiB SRAM cache memory.

Other uses of Pentium trademark

Pentium III chip mounted on a motherboard

Intel has retained the Pentium trademark for naming later variants and even generations of processor architectures, which are internally quite different from the Pentium itself:

It can be seen from this that brand name is only loosely related to the nature of a CPU's microarchitecture. The Pentium brand is traditionally used for desktop and notebook parts, the Celeron brand is used for "value" parts (typically lower performance and lower price), and the Xeon brand is used for high-performance parts suitable for servers and workstations. The same basic microarchitecture may be used for all brands, but implementations may differ in clock speeds, cache sizes, and package and sockets. Moreover, the same name is used for chips with unrelated microarchitectures.

The Intel Core processor uses the same microarchitecture as the Pentium M processors, but discards the Pentium M name (and also uses Intel's new logo). However the Pentium name will continue to be used in a new line of processors based on the Intel Core microarchitecture. These processors, codenamed Allendale, will be marketed as the Pentium E series. The new Pentium will have 1 MiB of L2 cache and use a 533 MHz (mobile) or 800 MHz (desktop) FSB, Intel 64 technology, and Execute Disable Bit, and will be a dual-core processor.

5th generation x86 competitors

See also

References

  1. ^ "Intel® Pentium® Dual-Core Processor". Intel. Retrieved 2007-12-13.
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