Unit I- Introduction to Microprocessor 8088/8086
Objectives:
1.
2.
3.
4.
5.
6.
Define what is a microprocessor.
Discuss the history of microprocessor.
Identify the categories of
Explain the role of microprocessor
Draw the structure of a microprocessor
Explain the function of data bus, address bus, and control bus.
The Microprocessor
The silicon chip that contains the CPU where most calculations take place
Microprocessors are distinguished by 3 characteristics
Instruction set: the set of instructions that the microprocessor can execute
Bandwidth: the number of bits processed in each instruction
Clock speed: (MHz) It determines how many instructions/second the processor can
execute
The Microprocessor
The brain or engine of the PC is the processor (sometimes called microprocessor), or
central processing unit (CPU). The CPU performs the system's calculating and processing.
Brief History
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Intel is generally credited with creating the first microprocessor in
1971 with the
introduction of a chip called the 4004.
All PC-compatible systems use either Intel processors or Intel-compatible processors
from a handful of competitors
Example: AMD or Cyrix.
Late 1970s the two most popular processors for PCs were not from Intel (although one
was a clone of an Intel processor). Personal computers of that time primarily used the Z80 by Zilog and the 6502 by MOS Technologies.
Z-80 was noted for being an improved and less expensive clone of the Intel 8080
processor, similar to the way companies today such as AMD, Cyrix, IDT, and Rise
Technologies have cloned Intel's Pentium processors.
Intel
1971 - 4004
First microprocessor
All CPU components on a single chip
4 bit
Followed in 1972 by 8008
8 bit
Both designed for specific applications
1974 - 8080
Intel’s first general purpose microprocessor
Pentium Evolution
8080
first general purpose microprocessor
8 bit data path
Used in first personal computer – Altair
8086
much more powerful
16 bit
instruction cache, prefetch few instructions
8088 (8 bit external bus) used in first IBM PC
80286
16 Mbyte memory addressable
up from 1Mb
80386
32 bit
Support for multitasking
80486
sophisticated powerful cache and instruction pipelining
built in maths co-processor
Pentium
Superscalar
Multiple instructions executed in parallel
Pentium Pro
Increased superscalar organization
Aggressive register renaming
branch prediction
data flow analysis
speculative execution
Pentium II
MMX technology
graphics, video & audio processing
Pentium III
Additional floating point instructions for 3D graphics
Pentium 4
Note Arabic rather than Roman numerals
Further floating point and multimedia enhancements
Itanium
64 bit
Categories of microprocessor
Processors can broadly be divided into the categories of: CISC, RISC, hybrid, and special
purpose.
Complex Instruction Set Computers (CISC)
have a large instruction set, with hardware support for a wide variety of operations. In
scientific, engineering, and mathematical operations with hand coded assembly language (and
some business applications with hand coded assembly language), CISC processors usually perform
the most work in the shortest time.
Categories of microprocessor
Reduced Instruction Set Computers (RISC)
have a small, compact instruction set. In most business applications and in programs
created by compilers from high level language source, RISC processors usually perform the most
work in the shortest time.
Hybrid
processors are some combination of CISC and RISC approaches, attempting to balance the
advantages of each approach.
Special purpose
processors are optimized to perform specific functions. Digital signal processors and
various kinds of co-processors are the most common kinds of special purpose processors.
Role of The Microprocessor
Fetch the Instruction from the memory
Fetch the operands of the Instruction
Decode the Instruction
Execute the Instruction
Output the results
CPU continuously does the (Fetch-Decode-Execute) Cycle
Role of The Microprocessor
To coordinate the functioning of the various components of the system by generating and
responding to control signals and to perform various arithmetic and logic functions.
Microprocessor Architecture
Basic Components
CPU Registers
special memory locations constructed from flip-flops and implemented on-chip
e.g., accumulator, count register, flag register
Arithmetic and Logic Unit (ALU)
ALU is where most of the action take place inside the CPU
Bus Interface Unit (BIU)
responsible for controlling the address and data busses when accessing main
memory and data in the cache
Control Unit and Instruction Set
CPU has a fixed set of instructions to work on, e.g., MOV, CMP, JMP
CPU Structure - Top Level
System Architecture
Address Bus - provides a memory address to system memory and I/O address to system I/O
devices
Data Bus transfers - data between the microprocessor and the memory and I/O attached to the
system
Control Bus provides control signals that cause memory or I/O devices to perform a read or
write operation
A19
Address Bus
A0
8086
System
Data Bus
(16 bit)
Control Bus
D15
To memory
D0
and I/O
RD/WR
Memory
I/O
Evaluation:
1. Identify the latest processor produced by Intel.
2. Draw and label the top level structure of microprocessor. Describe each component.
3. Differentiate the types of buses.
Objectives:
1. Draw and explain the internal block diagram of CPU.
2. Calculate maximum address in a memory.
3. Identify data types stored in memory.
The 8086 family of Microprocessors
Processor Data and Address Bus Sizes
Examples
Memory
Microprocessor addresses a maximum of 2n different memory locations, where n is a
number of bits on the address bus
Logical Memory
80x86 supports byte addressable memory
byte (8 bits) is a basic memory unit
e.g., when you specify address 24 in memory, you get the entire eight bits
when the microprocessors address a 16-bit word of memory, two consecutive
bytes are accessed
Physical Memory
The physical memories of 80x86 family differ in width
e.g., 8088 memory is 8 bits wide,
8086, 80286 memory is 16 bits wide, and
80386dx, 80486 memory is 32 bits wide
for programming there is no difference in memory width, because the logical
memory is always 8-bit wide
memory is organized in memory banks
a memory bank is an 8-bit wide section of the memory
e.g., the 16-bit microprocessors contain two memory banks to form 16-bit
wide section of memory that is addressed as bytes or words
The Memory Subsystem
What is a memory location?
The 80x86 family support Byte Addressable Memory (a byte is the basic memory
unit)
With an address bus of size n, the processor can address a maximum of 2n memory
locations
ex:ample: with 20, 24, and 32 address lines, the 80x86 can address 1Mbyte,
16Mbytes, and 4Gbytes
The Memory Subsystem
32 bit Processors
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32 bit processors (80386, 80486, and Pentium) use four banks of memory connected to
the 32 bit data bus
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Can access a double word in a one memory operation
Memory
Data Types
Numbers
bit (e.g., 1) ; nibble = 4 bits
DB: byte = octet = 8 bits
DW: Word = 2 bytes = 16 bits (80x86 terminology)
DD: DoubleWord = 4 bytes = 32 bits (80x86 terminology)
Intel uses little endian format (i.e., LSB at lower address)
Signed Integers (2's complement)
Text
Letters and characters (7-bit ASCII standard), e.g., 'A'=65=0x41
Extended ASCII (8-bit) allows for extra 128 graphics/symbols)
Collection of characters = Strings
Collection of Strings = Documents
Programs
Commands (MOV, JMP, AND, OR, NOT)
Collections of commands = subroutines
Collection of subroutines = programs
Floating point numbers
Images (GIF, TIF, JPG, BMP)
Video (MPEG, QuickTime, AVI)
Audio (voice, music)