Pentium
From Free net encyclopedia
Image:Pentium logo.png The Pentium is a fifth-generation x86 architecture microprocessor by Intel. First shipped on March 22, 1993, it is the successor to the 486 line. The Pentium was originally to be named 80586 or i586, but due to an ongoing battle with Advanced Micro Devices over the use of the previous processor generations' names--80386 and 80486--and the inability to trademark a number, Intel enlisted the help of Lexicon Branding in order to rename their new processor line. i586 is used in programming reference and parlance though, referring to all the early Pentium processors, and processors that are feature-compatible with the Pentium made by Intel's competitors.
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Major changes from the 486
- 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.
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 | P54 | P54C | P55C | P55C (Tillamook) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Process size (µm) | 0.80 | 0.60 | 0.35 | 0.25 | ||||||||||||||
| Clock speed (MHz) | 60 | 66 | 75 | 90 | 100 | 120 | 133 | 150 | 166 | 200 | 166 | 200 | 233 | 200 | 233 | 266 | 300 | |
| 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 | 1.8 | 1.8 | 1.8 | 1.8 | |
| Introduced | March 1993 | Oct. 1994 | March 1994 | March 1995 | June 1995 | Jan. 1996 | June 1996 | Oct. 1996 | June 1997 | Sept. 1997 | Jan. 1998 | Jan. 1999 | ||||||
P5, P54, P54C
Image:Pentium-mmx.jpg 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.
P55C, Tillamook
Image:Pentium-mmx1.jpg Subsequently, the P55C was enhanced by Intel's Research & Development Center in Haifa, Israel, to become the Pentium with MMX Technology (usually just called Pentium MMX); it was based on the P5 core, the 0.35 µm process was also used for this series, but it had a new set of 57 "MMX" instructions to improve working on multimedia tasks, such as encoding and decoding media. Mathematically, most of the MMX instructions provided improved support for vectors, matrices and arrays - complex calculations at the core of multimedia as well as much scientific work. However, software must be specially optimized to make use of MMX, and the increased speed the P55C showed at its launch was mainly due to the fact that the internal cache had been doubled in size to 32 KB. "MMX" is a reference to "Multi Media eXtension"
Tillamook (named after a city in Oregon) is Intel's version of the P55C for laptop computers. It was designed around a "Mobile Module" technology that contained the processor, 512 KB of secondary cache, and the 430TX northbridge chipset.
Other uses of Pentium trademark
Image:Pentium III on motherboard.jpg Intel has retained the Pentium trademark for naming later 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 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.
With the recent release of the Intel Core processors, Intel appears to be moving away from the Pentium brand name.
See also
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Intel 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 | Xeon | Core | Itanium | Itanium 2 (italics indicate non-x86 processors) |