The PR (performance rating, P-rating, or Pentium rating) system was a

figure of merit A figure of merit (FOM) is a performance metric that characterizes the performance of a device, system, or method, relative to its alternatives. Examples *Absolute alcohol content per currency unit in an alcoholic beverage *accurizing, Accuracy o ...

developed by

AMD Advanced Micro Devices, Inc. (AMD) is an American multinational corporation and technology company headquartered in Santa Clara, California and maintains significant operations in Austin, Texas. AMD is a hardware and fabless company that de ...

Cyrix 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. Ter ...

, IBM Microelectronics and

SGS-Thomson STMicroelectronics NV (commonly referred to as ST or STMicro) is a European multinational semiconductor contract manufacturing and design company. It is the largest of such companies in Europe. It was founded in 1987 from the merger of two st ...

in the mid-1990s as a method of comparing their

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...

processors to those of rival

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, and Delaware General Corporation Law, incorporated in Delaware. Intel designs, manufactures, and sells computer compo ...

. The idea was to consider

instructions per cycle In computer architecture, instructions per cycle (IPC), commonly called instructions per clock, is one aspect of a processor's performance: the average number of instructions executed for each clock cycle. It is the multiplicative inverse of c ...

(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.

Branding

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 Pentium is a series of x86 architecture-compatible microprocessors produced by Intel from 1993 to 2023. The Pentium (original), original Pentium was Intel's fifth generation processor, succeeding the i486; Pentium was Intel's flagship proce ...

running at 75 MHz. The designation "P75" was added to the chip to denote this. Later that year,

also adopted the PR system for its 6x86 and 6x86MX line of processors. 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. 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. 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 Pentium 4 is a series of single-core central processing unit, CPUs for Desktop computer, desktops, laptops and entry-level Server (computing), servers manufactured by Intel. The processors were shipped from November 20, 2000 until August 8, 20 ...

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 The megahertz myth, or in more recent cases the gigahertz myth, refers to the misconception of only using clock rate (for example measured in megahertz or gigahertz) to compare the performance of different microprocessors. While clock rates are a ...

. 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". ''

Maximum PC ''Maximum PC'', formerly known as ''boot'', was an American magazine and website published by Future US. It focuses on cutting-edge PC hardware, with an emphasis on product reviews, step-by-step tutorials, and in-depth technical briefs. Compon ...

'' 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.

References

{{reflist

External links

Processor Performance Rating (P-rating) Specification
February 1996. Uses Winstone 96.
P-rating
on wikichip AMD Rating systems Computer performance

Branding

See also

References

External links