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Pentium MMX

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The Pentium is a fifth-generation x86 architecture microprocessor by Intel employee Vinod Dahm which 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 the name was changed to Pentium (presumably because "pent-" means "five") because numbers could not be trademarked. i586 is used in programming though, referring to all the early Pentium processors, and Pentium-like processors made by Intel's competitors.

Major changes from the 486Edit

  • 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-Bit 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 66MHz and 60MHz. Later on 75, 90, 100, 120, 133, 150, 166, 200, and 233MHz versions gradually became available. 266 and 300MHz versions were later released for mobile computing. Pentium OverDrive processors were released at speeds of 63 and 83MHz 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 (Megahertz/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, P54CEdit

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 60-100MHz 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 66Mhz 0.8 µm versions of the Pentium processors were also known for their fragility and their (for the time) high levels of heat production. The heat problems were removed with the P54, which ran at a much lower voltage.

P55C, TillamookEdit

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. 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 32KB.

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, 512KB of secondary (L2 cache, and the 430TX northbridge chipset.

Intel CPU List
Intel CPU List:

Early: 4004 | 8008 | 8080 | 8085 x86: 8086 | 8088 | 186 | 286 | 386 | 486

Pentiums: Pentium | Pentium MMX | Pentium Pro | Pentium II | Pentium III | Pentium 4 | Pentium 4 Extreme Edition

Budget: Celeron | Celeron D

Xeons: Pentium II Xeon | Pentium III Xeon | Xeon | Xeon MP

Itaniums: Itanium | Itanium II

Mobile: Pentium M | Pentium 4 M | Celeron M

Dual-Core: Pentium D | Pentium Extreme

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