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

Intel 80386DX

The Intel 80386DX was the first true 32-bit processor used on the PC platform. Its internal register size was increased to 32 bits, and its data and address buses were as well, doubling data path width to the processor and increasing addressable memory to 4 GB theoretical. The 80386 family of chips offered more performance than the 80286s they replaced, largely through processor speed increases. The 386 did not offer the very large improvements over the 286 that the 286 did over the 8088.

The 386DX's increased power and the improved processor modes it offered (including full protected mode and virtual real modes) spurred the introduction of GUI-based operating systems on the PC, such as Microsoft Windows (although they are still quite slow on 386 chips). The instruction set of the 386 has set the standard for what is now called "x86" and hasn't changed very much since it was introduced. The 80386DX was the first to use pipelining to allow much improved processor performance through the use of much higher clock frequencies.

Invented by Intel, the 386 was also "cloned" by AMD and Cyrix. These are very good copies with no real compatibility problems. Intel only produced the 386DX up to 33 MHz (presumably to prevent overlapping into the 486's performance range) while AMD and Cyrix produced a 40 MHz version as well. This latter chip produced very good performance (for the time), comparable to many lower-end 486s. They are still however obsolete by today's standards, of course.

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

General Information

Manufacturer

Intel

Intel, AMD, Cyrix

AMD, Cyrix

Family Name

80386DX

Code name

--

Processor Generation

Third

Motherboard Generation

Third

Version

80386DX
-16

80386DX
-20

80386DX
-25

80386DX
-33

80386DX
-40

Introduced

Oct. 1985

Feb. 1987

April 1988

April 1989

!?

Variants and Licensed Equivalents

!?

Speed Specifications

Memory Bus Speed (MHz)

16

20

25

33

40

Processor Clock Multiplier

1.0

Processor Speed (MHz)

16

20

25

33

40

"P" Rating

--

 

Benchmarks

iCOMP Rating

~29

~38

49

68

~85

iCOMP 2.0 Rating

--

Norton SI

~15

~20

~25

35

~43

Norton SI32

!?

CPUmark32

--

Physical Characteristics

Process Technology

CMOS

Circuit Size (microns)

originally 1.5, now 1.0

Die Size (mm^2)

!?

Transistors (millions)

0.275

Voltage, Power and Cooling

External or I/O Voltage (V)

5

Internal or Core Voltage (V)

5

Power Management

None

Cooling Requirements

None

Packaging

Packaging Style

132-Pin PGA

Motherboard Interface

132-Pin Socket

External Architecture

Data Bus Width (bits)

32

Maximum Data Bus Bandwidth (Mbytes/sec)

63.6

76.3

95.4

127.2

152.6

Address Bus Width (bits)

32

Maximum Addressable Memory

4 GB

Level 2 Cache Type

None

Level 2 Cache Size

--

Level 2 Cache Bus Speed

--

Multiprocessing

No

Internal Architecture

Instruction Set

x86

MMX Support

No

Processor Modes

Real, Protected, Virtual Real

x86 Execution Method

Native

Internal Components

Register Size (bits)

32

Pipeline Depth (stages)

4

Level 1 Cache Size

None

Level 1 Cache Mapping

--

Level 1 Cache Write Policy

--

Integer Units

1

Floating Point Unit / Math Coprocessor

Optional 80387 Coprocessor

Instruction Decoders

1

Branch Prediction Buffer Size / Accuracy

None

Write Buffers

None

Performance Enhancing Features

None

Next: Intel 80386SX


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