Intel 80386 User Manual

CHAPTER 1
SYSTEM OVERVIEW
The 80386 is a new 32-bit microprocessor that forms the basis for a high-performance
32-bit system. The
80386 incorporates multitasking support, memory management, pipelined
architecture, address translation caches, and a high-speed bus interface all
on one chip. The
integration
of these features speeds the execution of instructions and reduces overall chip
count for a system. Paging and dynamic
data bus sizing can each be invoked selectively,
making the
80386 suitable for a wide variety of system designs and user applications.
While the
80386 represents a significant improvement over previous generations of micro-
processors, substantial ties to the earlier processors are preserved. Software compatibility
at
the object-code level is provided, so that an existing investment in 8086 and 80286 software
can be maintained. New software can be built upon existing routines, reducing the time to
market for new products. Hardware compatibility
is preserved through the dynamic bus-
sizing feature.
The major components of an
80386 system and their functions are shown in Figure 1-1.
Table
1-1 describes these components.
1.1 MICROPROCESSOR
The 80386 provides unprecedented performance. At 20 MHz, the 80386 is capable of
executing
at sustained rates of over five million instructions per second, a speed comparable
to
that of most super minicomputers. This achievement is made possible through a state-of-
the-art design
that includes a pipelined internal architecture, address translation caches, and
a high-performance bus.
The 80386 features 32-bit wide internal and external data paths and eight general-purpose
32-bit registers. The instruction set offers 8-, 16-, and 32-bit data types, and the processor
outputs 32-bit physical addresses directly, for a physical memory capacity of four gigabytes.
Table 1-1. 80386 System Components
Component Description
80386 Microprocessor 32-bit high-performance microprocessor with on-
chip memory management and protection
80287
or 80387 Numeric Coprocessor Performs numeric instruction in parallel with
80386; expands instruction set
82380
Integrated System Peripheral Provides 32-bit high-speed direct memory access,
interrupt control,
and interval timers
82385 Cache
Controller
Provides cache directory and management logic
82384 Clock Generator Generates system clock and RESET signal
8259A Programmable
Interrupt Controller Provides interrupt control and management
82258 Advanced DMA Performs direct memory
controller access (DMA)
1-1

Intel 80386 Specifications

General

Clock Speed	12 MHz to 40 MHz
Transistor Count	275, 000
Addressable Memory	4 GB
Data Bus Width	32-bit
Instruction Set	x86
Introduction Date	October 17, 1985
Virtual Memory	Yes
Operating Modes	Real mode, Protected mode, Virtual 8086 mode
Manufacturer	Intel
Model	80386
Address Bus Width	32-bit
Voltage	5V
Manufacturing Process	1.5 µm
Cache	No on-chip cache
FPU	Optional (80387)
Bus Interface	32-bit
Process Technology	CHMOS III
Package	PGA