Basic introduction to Intel 8086 microprocessor.

1. INTRODUCTION TO
MICROPROCESSORS
Compiled by: Seble N.

2. What is Microprocessor?
 Is a clock-driven semiconductor made of millions
of microscopic array of electronic
circuits and electronic components (resistors,
capacitors, inductors…) that are diffused or
implanted to surface of small silicon chip
 its basic purpose is to take input, process it and then
provide appropriate output
 Examples
 Intel processors, AMD , PowerPC …
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3. Function of microprocessors
 A microprocessor performs three basic steps:
 First, it fetches an instruction from memory,
 Second, it uses decoding circuitry to determine what the
instruction means (i.e., identify the operations and the
devices involved in it) and
 Third, it executes the instruction
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4. Components of microprocessor
 ALU (Arithmetic/Logic Unit)
 performs all arithmetic and logic operations
 Control Unit
 Interprets the instructions and generates various timing and
control signals
 it controls the flow of data between the μ-processor and
memory & peripherals
 Registers
 A register is a very small & very fast memory that is built
into the CPU in order to store the current data and
instructions which are being executed by the CPU
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5. Modes of Processing
 Real Mode
 One program at a time
 Protected Mode
 Can run more than one program concurrently and protect them
from each other
 Virtual Mode
 The processor can swap portion of the memory to the hard disk;
in this way programs running concurrently will have more space
to operate
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6. Characteristics of microprocessors
 Instruction set
 the set of instructions that a microprocessor can understand
or execute
 Word length
 refers to the number of bits a processor can process at a
time
 Eg. a 4-bit processor means the ALU can perform a 4-bit data
operation at a time
 the longer the word length is the more powerful the
processor is and can process data at a faster speed as
compared to processor with shorter word length
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7. Characteristics of microprocessors
 Speed
 measured in HZ = 1cycle/second
 Some processors may complete a single instruction per
cycle, or may take one or more cycles
 a 2 GHZ CPU may compute 2 billion instructions per second,
if it is able to complete a single instruction in a single cycle
 but if it takes 2 cycles to complete a single instruction then it
is only able to compute 1 billion instructions per second
 Cache Size
 The size of the cache memory
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8. Characteristics of microprocessors …
 Size of registers
 refers to the number of bits a microprocessor’s register can
hold at a time
 the size of addressable memory is often determined by the
width of registers
 Data bus width
 Refers to the number of bits a data bus can carry at a time
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9. Classes of microprocessors
1. Complex instruction set computer (CISC)
 Often contain instructions that perform several different
tasks at a once
 Ex: Intel Processors
2. Reduced instruction set computer (RISC)
 are made according to the function in which the
microprocessor can carry out small things in a specific
command
 In this way these processors completes more commands at a
faster rate
 is simpler, smaller and faster
 Ex: PowerPC and ARM's Cortex chips
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10. Evolution of Microprocessors
 Computing technologies based on vacuum tubes and transistors
 In 1959, Fair child semiconductors invented the first integrated circuit
 In 1968, Gordan Moore, Robert Noyce & Andrew Grove founded
Intel(Integrated Electronics)
 In 1971, the first microprocessor, Intel 4004 was released
 In 1972, Intel released the first 8-bit microprocessor Intel 8008
 In 1976, MOS technologies introduced the Motorola 6502 an 8-bit
processor, used in Apple I and II
 In 1981, the first PC was created by IBM using intel’s 8088 microprocessor
 Several companies like Intel, AMD, IBM, ARM, Motorola… make general
purpose processors that are designed for personal computers, laptops,
mobile devices and large central servers
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11. Intel microprocessors
 Intel
 is generally regarded as the company that sets the
benchmark for others to follow
 From the earlier Pentium and Centrino microprocessors to the
Core 2, Core i series
 Atom chips for mobiles
 The high-end Itanium and Xeon processors for server
applications
 Over 90% of laptops use Intel microprocessors
 HP, Dell, Apple, Samsung, Sony, Toshiba …
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12. Top CPU manufacturers
 Intel
 AMD
 Qualcomm
 Mediatek
 NVIDIA
 IBM
 Samsung
 Motorola
 Hewlett-Packard (hp)
 Dell
 Acer
 …
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13. Intel microprocessors
 Intel 4004
 Intel 8080
 Intel 8085
 Intel 8088
 Intel 8086
 Intel 80286
 Intel 80386
 Intel 80486
 Pentium
 Pentium II and III
 Dual Core/ Core
 Core i3, i5, i7
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14. Intel microprocessors …
4-bits processors
 Intel 4004
 1971- the first commercially available
processor as well as the first complete
CPU on a single chip
 a 4-bit processor: able to operate on 4
bits of data at a time
 4-bit data bus
 had 2,300 transistors
 clock speed of 108KHZ
 640 bytes addressable memory
 was designed for use in calculator but also
used traffic light controller, Blood
analyzers …
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15. Intel microprocessors …
8-bits processors
 Intel 8008
 first 8-bit microprocessor
 200KHz clock speed and 3,500 transistors,
 had 6 , 8-bit registers
 8-bit data bus
 can address up to 16KB
 Intel 8085
 was popular as an embedded controller
 ran at 5MHZ and contained 6500 transistors
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16. Intel microprocessors …
16-bits processors
 Intel 8086
 1978,16-bit: all registers, internal and external buses
 Used 20-bit addressing
 Can address 1 million bytes of internal memory
 29,000 transistors, 5MHz initially
 Intel 8088
 was identical to the 8086 with the exception of its 8-bit
internal bus
 The IBM 5150, the first IBM PC, came with the 8088
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17. Intel microprocessors …
16-bits processors
 Intel 80286
 can operate on real and protected mode
 134,000 transistors, 6M-8MHz initially
 can address up to 16 million bytes of internal memory
 was popular in IBM-PC AT and AT PC clones
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18. Intel microprocessors …
32-bits processors
 Intel 80386
 the first 32-bit microprocessor
 32 bit registers & data bus
 can operate on protected mode and supports virtual
mode
 275,000 transistors, 12MHz initially, later 33MHz
 Intel continued to manufacture the 80386 family until
September of 2007
 Intel single-source production of 386 to AMD
 Later changed in 1991 by AMD as AM386
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19. Intel microprocessors …
32-bits processors
 Intel 80486
 32 bit registers and data bus
 has a high speed cache memory, 8KB SRAM cache
 was launched with 25 to 50 MHz, included 1.2 million
transistors
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20. Intel microprocessors …
32-bits processors
 Pentium (Pentium I)
 32 bit registers, 64 bit data bus
 Has a high speed cache memory
 It can execute more than one instruction per clock cycle
 Pentium II and III
 Have a dual independent bus that provides separate
path to the system cache and memory
 On-die L2 cache
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21. Intel microprocessors …
64-bits processors
 New instruction set, not at all related to x86.
 Itanium
 Released May 29, 2001
 733 MHz to 800 MHz
 2MB cache
 Itanium 2
 Released July 2002
 900 MHz – 1.6 GHz
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22. Intel microprocessors …
64-bits processors
 Intel core 2
 x86-64 microprocessor
 Two cores on one die
 Number of transistors: 291 million
 64 KB of L1 cache per core
 1.86-3.00 GHz
 Intel core i series
 Intel core i3, i5, i7
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23. Reading Assignment 1
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 Micro-processor vs micro-controller
 Multi-core processor vs multi-processor
 CPU vs GPU
 Multi-threading and hyper-threading
 Overclocking

24. What is an x86 architecture?
 x86 is a family of backward compatible instruction set
architectures based on the Intel 8086 CPU
 the term "x86" came into being because the names of
several successors to Intel's 8086 processor end in "86",
including the 80186, 80286, 80386 and 80486 processors
 all newer processors using Intel's x86 instruction set are still
referred to as x86, i386, or i686 compatible (which means
they all use extensions of the original 8086 instruction set)
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25. Intel 8086
 1978, first x86 family microprocessor
 16-bit: all registers, internal and external buses
 can address 1 million bytes of internal memory
 used 20-bit addressing
 to date backward compatibility has been maintained
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26. 8086 Microprocessor Architecture
 The Basic Architecture of the Intel 8086
 The processor is partitioned into two logical units
 Execution Unit (EU)
 Bus Interface Unit(BIU)
 Why partition is needed?
 Because the processor runs considerably faster than
memory
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27. Architecture of 8086
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28. Execution Unit
 takes care of the processing including arithmetic and
logic operations
 its role is to execute instructions
 Contains
 ALU,
 Control Unit and
 Registers
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29. Bus Interface Unit (BIU)
 Its role is to deliver instructions and data to the EU
 Function
 to manage the bus control unit, segment registers and
instruction queue
 to provide access to instructions from memory and place
them in an instruction queue, which varies in size depending
on the processor
 This feature enables the BIU to look ahead and prefetch instructions
so that there is always a queue of instructions ready to execute
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30. Internal Memory of 8086
 Memory consists of cells organized in 8-bit
groups
 Bytes in memory are numbered consecutively,
beginning with 00
 8086
 was able to address 1MB of memory
 has 20bits wide memory address
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31. Intel 8086- Memory
 RAM
 From the 1MB of memory, the first
640K is base RAM
 is used for temporary program
storage
 ROM
 The 8086 Basic Input/Output System
(BIOS) begins at address 768K and
handles
 I/O devices, such as a hard disk
controller
 ROM beginning at 960K controls the
computer’s basic functions
 Power-On Self-Test, dot patterns for
graphics, and the disk self-loader
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32. Memory Segments
 Memory segmentation is the division of computer's
primary memory into segments or sections
 Segments are special areas defined in a program for
containing the code, the data, and what is known as the
stack
 A segment begins on a paragraph boundary, that is, at
a location evenly divisible by 16, or hex 10.
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33. Memory Segments …
 In real mode, the three main segments are code, data, and
stack
 Code Segment:
 Contains the machine instructions to be executed
 The first executable instruction is at the start of this segment, and the
operating system links to that location to begin program execution
 Data Segment:
 Contains a program’s defined data, constants, and work areas
 Stack Segment:
 Contains any data and addresses that the program needs to save
temporarily for use on subroutines
 A program may contain one or more segments, which may
vary in size, and can be defined in any sequence
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34. 8086/8088 Registers
 The registers are categorized into two sets:
 Data registers
 are for calculations
 Address registers
 used to store memory addresses that point to locations in
memory where data will be retrieved or stored
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35. 8086/8088 Data Registers
 aka general purpose registers, these are
 AX - Accumulator register
 BX - Base register
 CX - Counter register
 DX - Data register
 each are 16-bit long and can also be accessed as two 8-bit
registers
 AX  AH & AL
 BX  BH & BL
 CX  CH & CL
 DX  DH & DL
 The 80386 introduced an extended 32-bit general purpose
registers named EAX, EBX, ECX and EDX
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36. 8086/8088 Data Registers
 AX register
 is used for operations involving input/output and arithmetic
 BX register
 given the name base register because it is the only general
purpose register that can be used as an index in indirect
addressing
 can also be used for computations
 CX register
 usually used to control the number of times a loop is repeated or
a value to shift bits left or right in bit shifting operations
 can also be used for computations
 DX register
 is used for operations involving input/output and most arithmetic
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37. 8086/8088 Address Registers
 Segment registers: used to store starting address of memory segments
 Code Segment register
 Data Segment register
 Stack Segment register
 Extra Segment register
 Index registers: used for indexed addressing and string operations
 Source Index register
 Destination Index register
 Pointer registers: used to store offset address within memory segments
 Instruction Pointer register
 Stack Pointer register
 Base Pointer register
 All the above address registers are 16-bit long in 8086/8088
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38. 8086/8088 Segment Registers
 CS register: used to hold starting
address of program’s code segment
 DS register: used to hold starting
address of program’s data segment
 SS register: used to hold starting
address of program’s stack segment
 ES register: used to hold starting
address of programmers defined
extra data segment
 FS and GS registers: additional
extra segment registers introduced
by the 80386
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39. 8086/8088 Pointer Registers
 IP (Instruction Pointer) register
 used to locate a specific location within the code segment
 used to hold offset address of the next instruction to be
executed
 SP (Stack Pointer) register
 used to hold offset address of the top of the stack segment
 points to the current word being processed in the stack
 BP (Base Pointer) register
 used to point to a specific location in the stack
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40. 8086/8088 Index Registers
 SI (Source Index) & DI (Destination Index) registers
 are used to locate a specific location within the data
segment
 both are used in string handling operations. In this
context, SI is associated with the DS register while DI is
associated with the ES register
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41. Flags Register
 Is the status register in Intel x86 microprocessors that shows the current
state of the processor
 In 8086 flags register is 16 bits wide, among which 9 are active
 They are modified automatically by the processor after instruction
execution, which allows to determine the type of the result and also
conditions to transfer control to other parts of the program
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42. Flags Register …
 The flags bits has two groups
 Status flags: reflect the result of an operation executed
by the processor
 SF, ZF, AF, CF, PF & OF
 Control flags: enable or disable certain operations of
the processor
 Trap flag (TF)
 Interrupt flag (IF)
 Direction flag (DF)
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43. Flags Register: Status Flags
 SF (Sign): Indicates the resulting sign of an arithmetic operation (0 =
positive and 1 = negative)
 ZF (Zero): Indicates the result of an arithmetic or comparison
operation (0 = nonzero and 1 = zero result)
 PF (Parity): indicates the number of 1-bits that result from an
operation. (0=even parity and 1 = odd parity)
 AF (Auxiliary Carry): contains a carry out of bit 3 into bit 4 in an
arithmetic operation
 OF (Overflow): indicates overflow of a high-order(leftmost) bit
following in a signed arithmetic operation
 CF(Carry): contains carries from a high-order bit following an
unsigned arithmetic operation; also contains the contents of the last bit
of a shift or rotate operation
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44. Flags Register: control flags
 The Interrupt Flag
 Indicates that external interrupts, such as keyboard entry, are to be
processed or ignored
 Clearing IF (IF=0) disables interrupts
 The Direction Flag
 Determines left or right direction for moving or comparing string
(character) data
 If DF=1, the string instruction will automatically decrement the pointer
 The Trap Flag
 Permits operation of the processor in single-step mode
 Setting TF (TF=1) puts the processor into single step mode for
debugging, where the processor automatically generates an internal
interrupt after each instruction, allowing a program to be inspected as it
executes instruction by instruction
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