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Computer Architecture &
Organization
T xtText Books: B ks:
Computer System Architecture, 3/e, M. Morris Mano, Pearson.
Computer Organization and Architecture, 8/e, William
Stallings, Pearson.
Reference:
Computer Organization, 5/e, Hamachar, Vranesic, TMH.p g , , , ,
Computer Organization and Architecture, V. Rajaraman, T.
Radhakrishnan, PHI Learning.
Computer Organization and Design, Pal Choudary, PHI.
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UNIT - I:
Computer System:
Computer components, computer function, interconnection
structures, Bus interconnection, arithmetic and logic unit,
integer representation, integer arithmetic, fixed point
representation floating point representationrepresentation, floating point representation.
UNIT - II:
Central Processing Unit:
Instruction Sets: Characteristics and addressing modes –
Machine instruction characteristics, Types of operands and
operatorsoperators, addressing modes, instruction formats, Assembly addressing modes instruction formats Assembly
language
Process Structure and Functions – Process organization,
register organization, instruction cycle, instruction pipelining.
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What is a computer?
A computer is a sophisticated electronic calculating machine that:
Accepts input information,
Processes the information according to a list of internally
stored instructions and
Produces the resulting output informationProduces the resulting output information.
Capabilities of a computer are:
Accepting information to be processed as input.
Storing a list of instructions to process the information.
Processing the information according to the list of instructions.
Providing the results of the processing as output.
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Traditional Block Diagram of a computer:
Arithmetic & Logic Unit
Central Processing Unit ogic Unit CPU (ALU)
Control Unit (CU)
Input Device
Output Device
CPU
Memory
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Functional units of a computer:
Input unit accepts information: •Human operators, •Electromechanical devices •Other computers
Arithmetic and logic unit(ALU): •Performs the desired operations on the input information as determined by instructions in the memory
Output unit sends Stores Control unit coordinates
Output
Input
Control
Arithmetic & Logic
I/O (^) Processor
Memory Instr Instr Instr Data Data
Output unit sends results of processing: •To a monitor display, •To a printer
various actions •Input, •Output •Processing
Stores information: •Instructions, •Data
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Input unit Binary information must be presented to a computer in a specific format. This task is performed by the input unit:
- Interfaces with input devices.
- Accepts binary information from the input devices.
- Presents this binary information in a format expected by the computer.
- Transfers this information to the memory or processor- Transfers this information to the memory or processor.
Input Unit
Memory
Real world Computer
Keyboard Audio input ……
Processor
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Output unit
•Computers represent information in a specific binary form. Output units:
- Interface with output devices.
- Accept processed results provided by the computer in specific binary form.
- Convert the information in binary form to a form understood by an output device.p
Output Unit
Memory
Computer (^) Real world
Printer Graphics display Speakers ……
Processor
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Arithmetic and logic unit (ALU)
Operations are executed in the Arithmetic and Logic Unit
(ALU).
Arithmetic operations such as addition, subtraction.
Logic operations such as comparison of numbersLogic operations such as comparison of numbers.
In order to execute an instruction, operands need to be
brought into the ALU from the memory.
Operands are stored in general purpose registers available in the ALU. Access times of general purpose registers are faster than the cache.
Results of the operations are stored back in the memory orResults of the operations are stored back in the memory or
retained in the processor for immediate use.
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Control unit
Operation of a computer can be summarized as:
Accepts information from the input units (Input unit). Stores the information (Memory). PProcesses the information (ALU). th i f ti (ALU) Provides processed results through the output units (Output unit).
Operations of Input unit, Memory, ALU and Output unit are
coordinated by Control unit.
Instructions control “what” operations take place (e.g. data
transfer, processing).
CControl t l unitit generatest titiming i signalsi l whichhi h d tdetermines i
“when” a particular operation takes place.
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Memory Classification:
Memory
Primary Main
Secondary Storage Auxiliary
Random Access
Sequential Access
Read/Write Read Only (RAM) (ROM)
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Memory unit
Memory unit stores instructions and data.
Recall, data is represented as a series of bits. To store data, memory unit thus stores bits.
Processor reads instructions and reads/writes data from/to the
memory during the execution of a program.memory during the execution of a program.
In theory, instructions and data could be fetched one bit at a time. In practice, a group of bits is fetched at a time. Group of bits stored or retrieved at a time is termed as “word” Number of bits in a word is termed as the “word length” of a computer.
In order to read/write to and from memory, a processor should
know where to look:
“Address” is associated with each word locationAddress is associated with each word location.
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Memory unit (contd.. 1)
Processor reads/writes to/from memory based on the
memory address:
Access any word location in a short and fixed amount of time based on the address. Random Access Memory (RAM) provides fixed access time i dindependent of the location of the word. d t f th l ti f th d Access time is known as “Memory Access Time”.
Memory and processor have to “communicate” with each
other in order to read/write information.
In order to reduce “communication time”, a small amount of RAM (known as Cache) is tightly coupled with the processor. Modern computers have three to four levels of RAM units with different speeds and sizes:different speeds and sizes: Fastest, smallest known as Cache Slowest, largest known as Main memory.
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Characteristics of Computer Memory System (Contd..)
Location
In CPU
Internal tInternal t o processorpr cess r
External to processor (peripheral device)
Capacity
Word size
- The natural unitThe natural unit of organizationf r anizati n
Number of words
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Characteristics of Computer Memory System (Contd..)
Unit of transfer
Internal
UsuallUsuall y governed by data bus widthverned b data bus idth
External
Usually a block which is much larger than a word
Addressable unit
Smallest location which can be uniquely addressed
Word internally
Cluster on disks
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Characteristics of Computer Memory System (Contd..)
Access Methods
Sequential --- e.g. tape
¾ Start at the beginning and read through in order
¾ Access time depends on location of data and previous
locationlocation
Direct --- e.g. disk
¾ Individual blocks have unique address
¾ Access is by jumping to vicinity plus sequential search
¾ Access time depends on location and previous location
Random --- e.g. RAM
¾ IndInd v dual addresses dent fy locat ons exactlyividual addresses identify locations exactly
Associative --- e.g. cache
¾ Data is located by a comparison with contents of a portion
of the store
¾ Access time is independent of location or previous access
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Characteristics of Computer Memory System (Contd..)
Performance
Access time
- Time between presenting the address and getting the valid
data
Memory Cycle timeMemory Cycle time
- Time may be required for the memory to “recover” before
next access
- Cycle time is access + recovery (maybe rewrite)
Transfer Rate
- Rate at which data can be moved
Physical characteristicsy
- Decay
- Volatility
- Erasable
- Power consumption 22
Harvard Architecture:
¾ Uses physically separate storage and signal pathways for instructions and data.
¾ Microcontroller (single-chip microcomputer) and DSP (Digital Signal Processor)
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Computer – Hardware & Software
Computer Hardware:
Hardware, equipment involved in the function of a computer. Computer hardware consists of the components that can be physically handled.
IInput t hhardware d consistssists off externalt l ddevices—that i s th t isis, componentsts outside of the computer's CPU—that provide information and instructions to the computer.
Output hardware consists of external devices that transfer information from the computer's CPU to the computer user.
Storageg hardware providesp permanentp storageg of information and programs for retrieval by the computer. The two main types of storage devices are disk drives and memory.
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Computer – Hardware & Software (Contd..)
Computer Software:
Software, computer programs; instructions that cause the hardware— the machines—to do work. The two primary software categories are operating systems (system software)software), whichwhich controlcontrol thethe workingsworkings ofof thethe computercomputer, andand application software, which addresses the multitude of tasks for which people use computers. System software handles such essential, as maintaining disk files and managing the screen, whereas application software performs word processing, database management, and the like. Network software, that is neither system nor application software, enables groups of computers to communicate. LL anguage software, which provides programmers with the tools theyft hi h id ith th t l th need to write programs.
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Computer – Firmware
Computer Firmware:
Firmware, software routines stored in read-only memory (ROM).
U likUnlike random access memory (RAM), read-only memory stays d ss (RAM) d l st s intact even in the absence of electrical power.
Startup routines and low-level input/output instructions are stored in firmware. It falls between software and hardware.
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Execution of an Instruction:
Steps involved in the execution of an instruction by a
processor:
Fetch an instruction from the memory. Fetch the operands. Execute the instructionExecute the instruction. Store the results.
Several issues:
Where is the address of the memory location from which the present instruction is to be fetched? Where is the present instruction stored while it is executed? Where and what is the address of the memory location from which the data is fetched?the data is fetched?
Basic processor architecture has several registers to assist in
the execution of the instructions.
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Instruction Cycle:
Execution of an instruction takes place in two phases:
Instruction fetch (FC). Instruction execute (EC). IC = FC + EC
Instruction fetch:
Fetch the instruction from the memory location whose address is in the Program Counter (PC). Place the instruction in the Instruction Register (IR).
Instruction execute:
Instruction in the IR is examined (decoded) to determine which operation is to be performed. Fetch the operands from the memory or registers. EE xecute the operation.h i Store the results in the destination location.
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Instruction Cycle:
Instruction Cycle with Interrupts:
Fetch Cycle Execute Cycle Interrupt Cycle
Interrupts
Start
Fetch next Instruction
Execute Instruction
Check for Interrupt; Process Interrupt
Stop
Interrupts enabled
p disabled
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Transfer of control via Interrupts:
User program
Interrupt handler
N -------------------
I -----------------------
I +1 -------------------
Interrupt P ------------------- Occurs here
M ---------------------- 34
Microcomputer:
ALU
Register Array
Input Output
System Bus
Control Unit
Memory
System Bus
Microcomputer System or system. ¾ Subsystem System Bus: Data Bus Address Bus Control bus
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Functions of Microprocessor: Microprocessor initiated operations. Internal Data Operations. External or peripheral initiated operations.
Microprocessor Initiated Operations:
MemoryMemory Read Read – Read data from memoryRead data from memory. Memory Write – Write data into memory I/O – Read – Accept Data from I/P Device. I/O Write – Send Data to O/P Device.. Step 1: Identify the location. Step 2: Transfer Data. Step 3: Provide necessary timing and Synchronization signals.. TT ypes of Transfers:f T f Memory to CPU CPU to Memory I/O to CPU CPU to I/O I/O to or from Memory (DMA) 38
Bus Interconnection Structure:
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Bus Interconnection Structure:
Data Lines
Provide a path for moving data between system modules. These lines, collectively, are called the data bus ThThe d tdata bbus ttypically i ll consistsi t off 8 168,16 or 3232 separatet lilines, ththe numbers of lines being transferred to as the width of the data bus. Each line carry only 1 bit at a time, the number of lines determines how many bits can transferred at a time - overall system performance.
Address Lines
Used to designate the source or destination of the data on the data bus The width of the address bus determines the maximum possible memory capacity of the system.
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