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[ The PC Guide | Systems and Components Reference Guide | The Processor | Processor Families ]

Explanation of Processor Summary Tables

This section describes each of the characteristics contained in the processor summary tables included for each processor. The table below is identical to those used for each CPU, except that an explanation is given for what each statistic means.

General notes on the data in the summary tables:

  • The benchmark values were obtained from many different sources. All numbers should be considered approximate, since system variations can cause a particular PC to score significantly above or below the benchmarks shown. This is more likely to happen with some benchmarks than others; see here for more on these benchmarks. Values with a "~" in front of them are extrapolated or approximated, or in general ones I feel less confident about. Benchmark values are provided for general guidance purposes only.
  • Items with the value "!?" are unknown.

General Information


The company or companies that manufacture the processor.

Family Name

The name of the processor family.

Code name

The code name that was/is used to refer to this processor.

Processor Generation

Processor generation, first to sixth.

Motherboard Generation

The generation of the motherboard that this processor runs on; this is normally the same as the processor generation but not always.


The particular name of each version of the processor family.


The date that the processor was introduced. Note that this is the release date of the processor, which doesn't always equal the date that systems with the processor in them were first available.

Variants and Licensed Equivalents

Some processors were manufactured by other companies under license from the original designer; these are listed here.

Speed Specifications

Memory Bus Speed (MHz)

The speed of the main system memory bus in MHz.

Processor Clock Multiplier

The multiplier value for the processor; the amount that is multiplied by the memory bus speed to get the processor speed.

Processor Speed (MHz)

The speed of the processor in MHz.

"P" Rating

For some processors, the "P rating", which is the manufacturer's claim of the performance level of the processor regardless of its internal clock speed.


iCOMP Rating

The processor's iCOMP benchmark. For Intel processors from the 80386 through the Pentium.

ICOMP 2.0 Rating

The iCOMP 2.0 benchmark for the processor, for Intel processors from the Pentium on.

Norton SI

The original Norton SI benchmark rating, also sometimes called Norton SI 8.0.

Norton SI32

The new Norton SI 32-bit benchmark rating for the processor.


The processor's Ziff-Davis WinBench 32-bit CPU benchmark.

Physical Characteristics

Process Technology

The process technology used in manufacturing the chip; usually CMOS or Bipolar CMOS.

Circuit Size (microns)

The circuit size in microns, reflecting the miniaturization level of the processor.

Die Size (mm^2)

The physical size of the actual silicon chip (not the package that it is placed in).

Transistors (millions)

The number of transistors used in making the chip; more complex processors use more transistors.

Voltage, Power and Cooling

External or I/O Voltage (V)

The external voltage level used by the processor to interface to the motherboard, also called I/O voltage.

Internal or Core Voltage (V)

The internal voltage used by the core of the processor; lower than the external voltage on newer processors.

Power Management

Power management protocol used by the processor, if any.

Cooling Requirements

The generally-accepted cooling method required for the processor. Note that this is not really "cast in stone"; some manufacturers use a larger passive heat sink instead of an active one with no problems.


Packaging Style

The packaging used for the processor, including the number of pins.

Motherboard Interface

The socket or slot style used to connect the processor to the motherboard.

External Architecture

Data Bus Width (bits)

The width of the data bus in bits.

Maximum Data Bus Bandwidth (Mbytes/sec)

The maximum theoretical bandwidth of the data bus, computed as (memory bus speed * data bus width) / 8 / 1.048576. Note that this assumes the ability to perform one transfer per clock cycle, and many older CPUs were not able to do this. The "1.048576" factor converts the term to true megabytes (2^20).

Address Bus Width (bits)

The address bus width in bits.

Maximum Addressable Memory

The maximum theoretical amount of memory that the processor can address (generally 2^n where n is the width of the address bus).

Level 2 Cache Type

The type of secondary cache used, motherboard, integrated or processor card.

Level 2 Cache Size

The secondary cache size. For processors that have the secondary cache on the motherboard a typical range is provided since the actual value in any system of course depends on the particular motherboard.

Level 2 Cache Bus Speed

The speed of the secondary cache. This is usually either the same as the memory bus speed or the processor speed.


Whether or not the processor can be used in a multiprocessing environment, and if so, how many can be used.

Internal Architecture

Instruction Set

The instruction set supported by the processor, including any extensions (other than MMX).

MMX Support

Whether or not the processor supports the MMX instruction set extension.

Processor Modes

The different processor modes supported.

x86 Execution Method

The execution method that the processor uses, either native or emulation.

Internal Components

Register Size (bits)

The width of the processor's internal registers, which indicates the processor's overall "size".

Pipeline Depth (stages)

The number of steps in the processor's internal pipelines.

Level 1 Cache Size

The size of the level 1 data and instruction caches.

Level 1 Cache Mapping

The associativity of the level 1 cache.

Level 1 Cache Write Policy

The write policy of the primary cache, either write-through or write-back (or both).

Integer Units

The number of integer execution units in the processor. This includes specialized branch and load/store units, as well as dedicated MMX units.

Floating Point Unit / Math Coprocessor

For processors that have a built-in FPU, says "Integrated". For those that use a separate coprocessor, indicates its name.

Instruction Decoders

The number and type of decoders used in the processor.

Branch Prediction Buffer Size / Accuracy

The number of entries in the branch target buffer and the claimed accuracy level of the branch prediction unit, for processors that use branch prediction.

Write Buffers

The number of write buffers used to hold execution results.

Performance Enhancing Features

Indicates any additional performance-enhancing features, such as out of order execution, speculative execution, register renaming, or superpipelining.

Next: First Generation Processors

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