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

Intel 80386SX

The 80386SX is a "lite" version of the 80386DX chip. It uses only a 16-bit data bus, the same external bus width as the 80286. It also only can address 16 MB of memory, like the 80286. The SX version of the 386 chip was in fact released well after the DX, and in some ways was intended to move the market away from the 286 since it had roughly the same interfaces but better performance. It was actually introduced several years after the DX.

Note: It is a common myth that the 80386SX can be substituted in place of an 80286 in a 286 motherboard. While the chips are compatible in terms of their external interfaces they use different packaging. A 386SX could be put into a 286 motherboard if a proper adapter were used.

The narrower data bus width of the 386SX creates a reduction in performance of about 20-25% compared to an equivalent-speed 386DX; a significant difference but not excessive. The 80386SX chip was a popular choice for the first small notebook computers, especially the 386SL variant that introduced the SMM power management features to the Intel line. The 386SX is still a 32-bit processor internally and will run 32-bit software (really slowly :^) ). It is available in speeds from 16 to 33 MHz; a 40 MHz version was not produced for the SX, and is also available in cloned versions from AMD and Cyrix.

The 386SX chip is today considered obsolete.

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

General Information

Manufacturer

Intel, AMD, Cyrix

Family Name

80386SX

Code name

"P9"

Processor Generation

Third

Motherboard Generation

Third

Version

80386SX
-16

80386SX
-20

80386SX
-25

80386SX
-33

Introduced

June 1988

Jan. 1989

June 1988

Oct. 1992

Variants and Licensed Equivalents

386SL (power management features)

Speed Specifications

Memory Bus Speed (MHz)

16

20

25

33

Processor Clock Multiplier

1.0

Processor Speed (MHz)

16

20

25

33

"P" Rating

--

Benchmarks

iCOMP Rating

22

32

39

56

iCOMP 2.0 Rating

--

Norton SI

~11

15

~20

~27

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 (0.855 for 386SL)

Voltage, Power and Cooling

External or I/O Voltage (V)

5

Internal or Core Voltage (V)

5

Power Management

SMM on 386SL only

Cooling Requirements

None

Packaging

Packaging Style

132-Pin PGA

Motherboard Interface

132-Pin Socket

External Architecture

Data Bus Width (bits)

16

Maximum Data Bus Bandwidth (Mbytes/sec)

31.8

38.1

47.7

63.6

Address Bus Width (bits)

24

Maximum Addressable Memory

16 MB

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: Fourth Generation Processors


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