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

Intel Pentium with MMX Technology OverDrive

With the introduction of the Intel Pentium with MMX Technology, Intel also created OverDrive processors to upgrade existing Pentium motherboards to the new MMX chip. Most older Pentium motherboards cannot handle the new Pentium with MMX because of its requirement for a 2.8V core. Keeping with the tradition of Intel's OverDrive line, the Pentium with MMX OverDrive includes a converter that lets it run in Socket 5 motherboards (except for the 200) and Socket 7s that do not have 2.8V support. Otherwise the chip is identical to the standard Pentium with MMX. Refer to the section on the Pentium with MMX for more description of its improvements over the Pentium. See the section on the Pentium Classic OverDrive for more on using OverDrive processors.

Note: In general, if your motherboard can support the MMX chip directly, it is almost always better to buy a real Pentium with MMX as opposed to an OverDrive, because they are typically less expensive. Your motherboard manual will tell you what your system's limitations are, but generally if your Pentium motherboard supports split-rail voltage, you should be able to run a standard Pentium with MMX.

The initial Pentium with MMX OverDrives run at 125 MHz, 150 MHz and 166 MHz, for use in Pentium 75 (1.5x50), Pentium 90 (1.5x60) and Pentium 100 (1.5x66) systems respectively. These chips replaced identical non-MMX OverDrives which Intel quickly phased out when MMX hit the market. In each case, the chip has a fixed clock multiplier of 2.5, intended for use in place of the older 1.5 multiplier chips on these three system speeds.

Intel later introduced two new Pentium with MMX OverDrives, running at 180 MHz and 200 MHz. These chips run with a 3x clock multiplier; the 180 is intended for upgrading 90, 120 and 150 MHz systems running at 60 MHz system bus speeds, and the 200 for upgrading 100, 133 and 166 systems running with 66 MHz system buses. No 3x clock multiplier OverDrive was created specifically for 50 MHz Pentium 75 systems, but the 180 will function in Pentium 75 systems, running at 150 MHz. (Note that the older 150 MHz OverDrive has a 2.5x multiplier and will only run at 125 in a Pentium 75 PC).

Note: Unlike the other OverDrives, which will work in either socket 5 or socket 7 motherboards, the Pentium with MMX OverDrive 200 is intended for use only in socket 7 systems.

These OverDrives provide significant performance improvements over the original chips and the ability to execute MMX software as well. It's still important to remember that increasing the performance of the processor is only part of the solution to increasing overall system performance. Many other factors impact on system performance, and increasing the processor clock while leaving the system bus speed the same is an exercise in diminishing returns, because the processor is increasingly stuck waiting for the rest of the system.

Look here for an explanation of the categories in the processor summary table below, including links to more detailed explanations.

General Information

Manufacturer

Intel

Family Name

Pentium With MMX Technology OverDrive

Code name

"P54CTB"

Processor Generation

Fifth

Motherboard Generation

Fifth

Version

Pentium with MMX OverDrive 125

Pentium with MMX OverDrive 150

Pentium with MMX OverDrive 166

Pentium with MMX OverDrive 180 Pentium with MMX OverDrive 200

Introduced

Jan. 1997

Mid 1997

Variants and Licensed Equivalents

--

Speed Specifications

Memory Bus Speed (MHz)

50

60

66

60 66

Processor Clock Multiplier

2.5

3.0

Processor Speed (MHz)

125

150

166

180 200

"P" Rating

~150

~180

~200

~215 ~240

Benchmarks

iCOMP Rating

~1200

~1400

~1575

~1700 ~1900

iCOMP 2.0 Rating

120

144

160

~167 182

Norton SI

~480

~570

~640

~670 ~770

Norton SI32

~36

~46

50.7

~53 57.5

CPUmark32

~290

340

378

~390 425

Physical Characteristics

Process Technology

CMOS

Circuit Size (microns)

0.35

Die Size (mm^2)

141

Transistors (millions)

4.5

Voltage, Power and Cooling

External or I/O Voltage (V)

3.3

Internal or Core Voltage (V)

2.8 (3.3 from Motherboard)

Power Management

SMM

Cooling Requirements

Active heat sink (included)

Packaging

Packaging Style

296-Pin SPGA

Motherboard Interface

Socket 5, Socket 7

Socket 7

External Architecture

Data Bus Width (bits)

64

Maximum Data Bus Bandwidth (Mbytes/sec)

381.5

457.8

508.6

457.8 508.6

Address Bus Width (bits)

32

Maximum Addressable Memory

4 GB

Level 2 Cache Type

Motherboard

Level 2 Cache Size

Usually 256 KB - 512 KB

Level 2 Cache Bus Speed

Same as Memory Bus

Multiprocessing

No

Internal Architecture

Instruction Set

x86 plus Pentium Extensions

MMX Support

Yes

Processor Modes

Real, Protected, Virtual Real

x86 Execution Method

Native

Internal Components

Register Size (bits)

32

Pipeline Depth (stages)

6

Level 1 Cache Size

16 KB Data, 16 KB Instruction

Level 1 Cache Mapping

4-Way Set Associative

Level 1 Cache Write Policy

Write-Through (Data and Instruction), Write-Back (Data Only)

Integer Units

4 (2 for MMX)

Floating Point Unit / Math Coprocessor

Integrated

Instruction Decoders

1

Branch Prediction Buffer Size / Accuracy

512 entries / 90%

Write Buffers

4

Performance Enhancing Features

--

Next: Cyrix 6x86 ("M1")


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