Pentium



The Pentium is a fifth-generation x86 architecture microprocessor from Intel, developed by Vinod Dham. It was the successor to the 486 line, and was first shipped on March 22, 1993.

The Pentium was originally to be named 80586 or i586, to follow the naming convention of previous generations. However, Intel was unable to convince 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 maintained through several generations of processors, from the Pentium Pro to the Pentium Extreme Edition. Intel has retired the brand and replaced it with the "Intel Core" brand. 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.

In programming, it is sometimes necessary to distinguish the original Pentium processor architecture from later Pentium-branded architectures. For these cases, i586 is often used to refer to all the early Pentium processors, as well as processors made by Intel's competitors that can run machine code targeted to the early Pentiums.

* 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 so-called 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 a few late-model AMD 486 parts were roughly equal to the Pentium 75.

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.

The original Pentium microprocessor had the internal code name P5, and was a pipelined in-order superscalar microprocessor, produced using a 0.8 µm process. It was followed by the P54, 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 P54 was followed by the P54C, 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 5V operation. The heat problems were removed with the P54, which ran at a much lower voltage (3.3V). P5 Pentiums used Socket 4, while P54 started out on Socket 5 before moving to Socket 7 in later revisions. All desktop Pentiums from P54C onwards used Socket 7. Another bug known as f00f bug was discovered soon, fortunately operating system vendors responded by implementing workarounds that prevented the crash.

The Pentium OverDrive for 486 systems, a sort of oddity among the other Pentium processors, was released in early 1995. The Pentium architecture had to be modified in many ways to operate on the 486 platform's narrower 32-bit data bus and slower cache architecture. As such, the chip came equipped with a 32 KB L1 cache, double the what a pre-P55C Pentium came equipped with. The chip also included an attached fan/heatsink assembly in addition to onboard power regulation to convert the frequent 5 volt power circuitry on 486 boards down to the Pentium's 3.3 volt needs.

The P55C 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 1 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.

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 Tillamook (named after a city in Oregon), the module also held the 430TX chipset along with the system's 512 KiB SRAM cache memory.

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

* Pentium Pro
* Pentium II
* Pentium III
* Pentium 4
* Pentium M
* Pentium D
* Pentium Extreme Edition

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); with the release of the Intel Core 2 processors on July 27, 2006, Intel has retired the Pentium name.Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.
Virtual Magic is a human knowledge database blog. Text Based On Information From Wikipedia, Under The GNU Free Documentation License. Copyright (c) 2007 Virtual Magic. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

Links to this post:

Create a Link

<< Home