The PR (performance rating, P-rating, or Pentium rating) system was a figure of merit developed by AMD, Cyrix, IBM Microelectronics and SGS-Thomson in the mid-1990s as a method of comparing their x86 processors to those of rival Intel. The idea was to consider instructions per cycle (IPC) in addition to the clock speed, so that the processors become comparable with Intel's Pentium that had a higher clock speed with overall lower IPC. [1] [2]
The first use of the PR system was in 1995, when AMD used it to assert that their AMD 5x86 processor was as fast as a Pentium running at 75 MHz. The designation "P75" was added to the chip to denote this. [3] : 3 Later that year, Cyrix also adopted the PR system for its 6x86 [1] and 6x86MX line of processors.[ citation needed ] These processors were faster than Pentiums of the same speed in some benchmarks, so Cyrix gave them a Performance Rating faster than their clock speed. [3] Some AMD K5 models also use the PR system.
AMD initially branded its AMD K6 processors with a "PR2" rating but dropped this after consumer confusion. [4] AMD revived the branding for its Athlon XP, which was released in 2001. The efficient Athlon XP chips could perform better than similarly-clocked chips from Intel's competing Pentium 4 line-up, which depended on high clock speeds to overcome their low IPC. As a result, AMD believed consumers would be swayed by the megahertz myth. [5] These chips were rated against the Athlon Thunderbird but were popularly compared to the Pentium 4. As a result, the branding became colloquially known as a "Pentium Rating". [3] : 6 Maximum PC criticized this as making it more difficult for power users to differentiate between the various Athlon XP chips. For example, two chips could be given the same "PR" branding but have much different engineering (cache size, bus speed, etc), which would affect their performance at different tasks. [6]
Advanced Micro Devices, Inc. (AMD) is an American multinational corporation and semiconductor company based in Santa Clara, California, that develops computer processors and related technologies for business and consumer markets.
Athlon is the brand name applied to a series of x86-compatible microprocessors designed and manufactured by AMD. The original Athlon was the first seventh-generation x86 processor and the first desktop processor to reach speeds of one gigahertz (GHz). It made its debut as AMD's high-end processor brand on June 23, 1999. Over the years AMD has used the Athlon name with the 64-bit Athlon 64 architecture, the Athlon II, and Accelerated Processing Unit (APU) chips targeting the Socket AM1 desktop SoC architecture, and Socket AM4 Zen (microarchitecture). The modern Zen-based Athlon with a Radeon Graphics processor was introduced in 2019 as AMD's highest-performance entry-level processor.
The Cyrix 6x86 is a line of sixth-generation, 32-bit x86 microprocessors designed and released by Cyrix in 1995. Cyrix, being a fabless company, had the chips manufactured by IBM and SGS-Thomson. The 6x86 was made as a direct competitor to Intel's Pentium microprocessor line, and was pin compatible. During the 6x86's development, the majority of applications performed almost entirely integer operations. The designers foresaw that future applications would most likely maintain this instruction focus. So, to optimize the chip's performance for what they believed to be the most likely application of the CPU, the integer execution resources received most of the transistor budget. This would later prove to be a strategic mistake, as the popularity of the P5 Pentium caused many software developers to hand-optimize code in assembly language, to take advantage of the P5 Pentium's tightly pipelined and lower latency FPU. For example, the highly anticipated first-person shooter Quake used highly optimized assembly code designed almost entirely around the P5 Pentium's FPU. As a result, the P5 Pentium significantly outperformed other CPUs in the game.
The Intel 486, officially named i486 and also known as 80486, is a microprocessor. It is a higher-performance follow-up to the Intel 386. The i486 was introduced in 1989. It represents the fourth generation of binary compatible CPUs following the 8086 of 1978, the Intel 80286 of 1982, and 1985's i386.
The K6 microprocessor was launched by AMD in 1997. The main advantage of this particular microprocessor is that it was designed to fit into existing desktop designs for Pentium-branded CPUs. It was marketed as a product that could perform as well as its Intel Pentium II equivalent but at a significantly lower price. The K6 had a considerable impact on the PC market and presented Intel with serious competition.
The Pentium is a x86 microprocessor introduced by Intel on March 22, 1993. It is the first CPU using the Pentium brand. Considered the fifth generation in the 8086 compatible line of processors, its implementation and microarchitecture was internally called P5.
Cyrix Corporation was a microprocessor developer that was founded in 1988 in Richardson, Texas, as a specialist supplier of floating point units for 286 and 386 microprocessors. The company was founded by Tom Brightman and Jerry Rogers.
Pentium 4 is a series of single-core CPUs for desktops, laptops and entry-level servers manufactured by Intel. The processors were shipped from November 20, 2000 until August 8, 2008. It was removed from the official price lists starting in 2010, being replaced by Pentium Dual-Core.
The Am5x86 processor is an x86-compatible CPU announced in November of 1995 by AMD for use in 486-class computer systems. It began shipping in December of 1995, with a base price of $93 per unit in bulk quantities. Before being released, it was in development under the codename "X5".
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