computer systems architecture - micronet international college

Computer Systems Architecture [ Unit 19]

Outcomes:

1. Understand how data can be represented within computer systems

2. Understand the functions of computer system components

3. Understand the principles of processor operations.

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Outcome 2: Understand the functions of computer system components

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Outcome 1 4

Key Components ▸ Central Processing Unit ▸ Memory ▸ Interfaces ▸ Buses ▸ Peripherals

Outcome 1

Central Processing Unit

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CPU

The central processing unit (CPU) is the unit which performs most of the processing inside a computer.

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CPU

To control instructions and data flow to and from other parts of the computer, the CPU relies heavily on a chipset, which is a group of microchips located on the motherboard.

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CPU

The CPU has two components: ▸ Control Unit ▸ Arithmetic Logic Unit (ALU)

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CPU

Control Unit Extracts instructions from memory and decodes and executes them

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CPU

Arithmetic Logic Unit (ALU) Handles arithmetic and logical operations

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CPU

To function properly, the CPU relies on the system clock, memory, secondary storage, and data and address buses.

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Multicore CPU

Multicore CPUs are also common, in which a single chip contains multiple CPUs. Multiple processors are ideal for intensive parallel tasks requiring multitasking.

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Multicore CPU

Each CPU has an independent interface, separate cache, and individual paths to the system front-side bus.

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CPU 14

Outcome 1 15

Key Components ▸ Central Processing Unit ▸ Memory ▸ Interfaces ▸ Buses ▸ Peripherals

Outcome 1

Computer Memory

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Memory

Computer memory is any physical device capable of storing information temporarily like RAM (random access memory), or permanently, like ROM (read-only memory).

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Memory Memory devices utilize integrated circuits and are used by operating systems, software, and hardware.

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Memory Types of Memory ▸ Volatile ▸ Non Volatile

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Memory Types of Memory ▸ Volatile ▸ Non Volatile

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Memory

Volatile memory A memory that loses its contents when the computer or hardware device loses power.

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Memory

Computer RAM is an example of a volatile memory and is why if your computer freezes or reboots when working on a program, you lose anything that hasn't been saved.

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Memory

Non-volatile memory, sometimes abbreviated as NVRAM, is a memory that keeps its contents even if the power is lost. Flash memory is an example of a non-volatile memory.

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Memory

Primary Storage: RAM Secondary Storage: Hard Drive

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Memory

Common Type of Memory ▸ SRAM ▸ DRAM

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Memory

Key Differences Between SRAM and DRAM. SRAM is an on-chip memory whose access time is small while DRAM is an off-chip memory which has a large access time. Therefore SRAM is faster than DRAM.

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Outcome 1 27

Key Components ▸ Central Processing Unit ▸ Memory ▸ Buses ▸ Interfaces ▸ Peripherals

Outcome 1

Computer Memory

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Outcome 1

Interfaces

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Interfaces

An interface is a shared boundary across which two or more separate components of a computer system exchange information. The exchange can be between software, computer hardware, peripheral devices, humans, and combinations of these.

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Interfaces

Some computer hardware devices, such as a touchscreen, can both send and receive data through the interface, while others such as a mouse or microphone may only provide an interface to send data to a given system.

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Place your screenshot here

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Types of Interfaces

1. Software

2. Hardware

Interfaces

Hardware interfaces exist in many of the components, such as the various buses, storage devices, other I/O devices, etc.

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Interfaces

A hardware interface is described by the mechanical, electrical and logical signals at the interface and the protocol for sequencing them (sometimes called signaling).

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Interfaces

A software interface may refer to a wide range of different types of interface at different "levels": an operating system may interface with pieces of hardware.

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Interfaces

Applications or programs running on the operating system may need to interact via data streams, filters, and pipelines; and in object oriented programs, objects within an application may need to interact via methods.

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Outcome 1

CPU Clock

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Clock Speed

Clock speed is the rate at which a processor can complete a processing cycle. It is typically measured in megahertz or gigahertz.

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Clock Speed

One megahertz is equal to one million cycles per second, while one gigahertz equals one billion cycles per second. This means a 1.8 GHz processor has twice the clock speed of a 900 MHz processor.

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Outcome 1

System Buses

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System Buses

The system bus is a pathway composed of cables and connectors used to carry data between a computer microprocessor and the main memory.

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System Buses

The bus provides a communication path for the data and control signals moving between the major components of the computer system.

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System Buses

The system bus works by combining the functions of the three main buses: namely, the data, address and control buses. Each of the three buses has its separate characteristics and responsibilities.

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System Buses

The system bus connects the CPU with the main memory and, in some systems, with the level 2 (L2) cache.

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System Buses

Other buses, such as the IO buses, branch off from the system bus to provide a communication channel between the CPU and the other peripherals.

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System Buses

Control Bus The control bus carries the control, timing and coordination signals to manage the various functions across the system.

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Clock Speed

Address Bus The address bus is used to specify memory locations for the data being transferred.

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Clock Speed

Data Bus The data bus, which is a bidirectional path, carries the actual data between the processor, the memory and the peripherals.

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Computer Memory


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1. Volatile 2. Non

Volatile

Types of Memory

Memory Cache

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Primary/Main Memory

Secondary Memory


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Cache Memory

Memory – Cache Memory

Cache Memory Cache memory is a very high speed semiconductor memory which can speed up the CPU. It acts as a buffer between the CPU and the main memory.

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Memory – Cache Memory Cache Memory It is used to hold those parts of data and program which are most frequently used by the CPU. The parts of data and programs are transferred from the disk to cache memory by the operating system, from where the CPU can access them.

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The advantages of cache memory ▸ Cache memory is faster than main memory. ▸ It consumes less access time as compared to main memory. ▸ It stores the program that can be executed within a short period of time. ▸ It stores data for temporary use.

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The disadvantages of cache memory ▸ Cache memory has limited capacity. ▸ It is very expensive.

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Main Memory

Memory – Main Memory

Primary memory holds only those data and instructions on which the computer is currently working. It has a limited capacity and data is lost when power is switched off.

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It is generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed resides in the main memory.

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Characteristics of Main Memory ▸ These are semiconductor memories. ▸ It is known as the main memory. ▸ Usually volatile memory. ▸ Data is lost in case power is switched off. ▸ It is the working memory of the computer. ▸ Faster than secondary memories. ▸ A computer cannot run without the primary

memory.

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Memory – Secondary Memory

This type of memory is also known as external memory or non-volatile. It is slower than the main memory. These are used for storing data/information permanently.

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CPU directly does not access these memories, instead they are accessed via input-output routines. The contents of secondary memories are first transferred to the main memory, and then the CPU can access it. For example, disk, CD-ROM, DVD, etc.

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Characteristics of Secondary Memory ▸ These are magnetic and optical memories. ▸ It is known as the backup memory. ▸ It is a non-volatile memory. ▸ Data is permanently stored even if power is switched

off. ▸ It is used for storage of data in a computer. ▸ Computer may run without the secondary memory. ▸ Slower than primary memories.

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Computer Processor

Computer Processor

The computer processor is referred as the brain of the computer systems.

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Computer Processor

The computer processor is referred as the brain of the computer systems.

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Processor – Interrupt vs Polling

VS. Interrupt Polling

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Interrupt and Polling are the two ways to handle the events generated by the devices that can happen at any moment while CPU is busy in executing another process.

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Polling and Interrupt let CPU stop what it is currently doing and respond to the more important task. Polling and Interrupt are different from each other in many aspects.

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But the basic point that distinguishes Polling and Interrupt is that in polling CPU keeps on checking I/O devices at regular interval whether it needs CPU service whereas, in interrupt, the I/O device interrupts the CPU and tell CPU that it need CPU service.

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Processor – Interrupt

An interrupt is a hardware mechanism that enables CPU to detect that a device needs its attention. The CPU has a wire interrupt-request line which is checked by CPU after execution of every single instruction.

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Processor – Interrupt

When CPU senses an interrupt signal on the interrupt-request line, CPU stops its currently executing task and respond to the interrupt send by I/O device by passing the control to interrupt handler. The interrupt handler resolves the interrupt by servicing the device.

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Processor – Polling

As we have seen in interrupts, the input from I/O device can arrive at any moment requesting the CPU to process it. Polling is a protocol that notifies CPU that a device needs its attention.

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Processor – Polling

Unlike in interrupt, where device tells CPU that it needs CPU processing, in polling CPU keeps asking the I/O device whether it needs CPU processing.

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Processor – Key Differences

▸ In interrupt, the device notifies the CPU that it needs servicing whereas, in polling CPU repeatedly checks whether a device needs servicing.

▸ Interrupt is a hardware mechanism as CPU has a wire,

interrupt-request line which signal that interrupt has occurred. On the other hands, Polling is a protocol that keeps checking the control bits to notify whether a device has something to execute.

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▸ Interrupt handler handles the interrupts generated by the devices. On the other hands, in polling, CPU services the device when they require.

▸ Interrupts are signalled by the interrupt-request line.

However, Command-ready bit indicate that the device needs servicing.

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▸ In interrupts, CPU is only disturbed when any device interrupts it. On the other hand, in polling, CPU waste lots of CPU cycles by repeatedly checking the command-ready bit of every device.

▸ An interrupt can occur at any instant of time whereas,

CPU keeps polling the device at the regular intervals.

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▸ Polling becomes inefficient when CPU keeps on polling the device and rarely finds any device ready for servicing. On the other hands, interrupts become inefficient when the devices keep on interrupting the CPU processing repeatedly.

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CPU Architecture

CPU Architecture

The terms 32-bit and 64-bit refer to the way a computer's processor (also called a CPU), handles information. The 64-bit version of Windows handles large amounts of random access memory (RAM) more effectively than a 32-bit system.

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CPU Architecture

Simply put, a 64-bit processor is more capable than a 32-bit processor, because it can handle more data at once. A 64-bit processor is capable of storing more computational values, including memory addresses, which means it’s able to access over four billion times the physical memory of a 32-bit processor.

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CPU Architecture 81


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Machine Code

Low Level Language

Low-level languages are designed to operate and handle the entire hardware and instructions set architecture of a computer directly.

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Low Level Language

Low-level languages are considered to be closer to computers. In other words, their prime function is to operate, manage and manipulate the computing hardware and components.

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Low Level Language

Programs and applications written in a low-level language are directly executable on the computing hardware without any interpretation or translation. Example of Low Level Languages

1. Machine Code 2. Assembly Programming

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Machine Code

A computer programming language consisting of binary or hexadecimal instructions which a computer can respond to directly.

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Assembly Language

An assembly language often abbreviated asm, is any low-level programming language in which there is a very strong correspondence between the program's statements and the architecture's machine code instructions

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Assembler

An assembler is a type of computer program that interprets software programs written in assembly language into machine language, code and instructions that can be executed by a computer.

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Assembler

An assembler is sometimes referred to as the compiler of assembly language. It also provides the services of an interpreter.

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Fetch Execute Cycle

Fetch-Decode-Execute cycle

The Fetch-Decode-Execute cycle of a computer is the process by which a computer: 1. Fetches a program instruction from its memory, 2. Determines what the instruction wants to do, 3. Carries out those actions.

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This cycle is repeated continuously by the central processing unit (CPU), from boot up to when the computer is shut down. In modern computers this means completing the cycle billions of times a second! Without it nothing would be able to be calculated.

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The circuits used in the CPU during the cycle are:

1. Program Counter (PC) 2. Memory Address Register (MAR) 3. Memory Buffer Register (MBR) 4. Instruction register (IR) 5. General Purpose Register

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Program Counter (PC) An incrementing counter that keeps track of the memory address of which instruction is to be executed next.

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Memory Address Register (MAR) The address in main memory that is currently being read or written

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Memory Buffer Register (MBR) A two-way register that holds data fetched from memory (and ready for the CPU to process) or data waiting to be stored in memory

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Instruction register (IR) A temporary holding ground for the instruction that has just been fetched from memory

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The contents of the Program Counter, the address of the next instruction to be executed, is placed into the Memory Address Register

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The contents of the Program Counter, the address of the next instruction to be executed, is placed into the Memory Address Register

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The address is sent from the MAR along the address bus to the Main Memory. The instruction at that address is found and returned along the data bus to the Memory Buffer Register. At the same time the contents of the Program Counter is increased by 1, to reference the next instruction to be executed.

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The MBR loads the Current Instruction Register with the instruction to be executed. The instruction is decoded and executed using the ALU if necessary. The Cycle starts again!

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Processor Architecture

RISC and CISC

The architecture of the Central Processing Unit (CPU) operates the capacity to function from “Instruction Set Architecture” to where it was designed. The architectural design of the CPU is Reduced instruction set computing (RISC) and Complex instruction set computing (CISC).

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RISC

What is RISC? A reduced instruction set computer is a computer which only uses simple commands that can be divided into several instructions which achieve low-level operation within a single CLK cycle, as its name proposes “Reduced Instruction Set”.

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RISC

This is small or reduced set of instructions. Here, every instruction is expected to attain very small jobs. In this machine, the instruction sets are modest and simple, which help in comprising more complex commands.

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RISC

Each instruction is of the similar length; these are wound together to get compound tasks done in a single operation. Most commands are completed in one machine cycle. This pipelining is a crucial technique used to speed up RISC machines.

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CISC

What is CISC? A complex instruction set computer is a computer where single instructions can perform numerous low-level operations like a load from memory, an arithmetic operation, and a memory store or are accomplished by multi-step processes or addressing modes in single instructions, as its name proposes “Complex Instruction Set ”.

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CISC

CISC Architecture The term CISC stands for ‘’Complex Instruction Set Computer’’. It is a CPU design plan based on single commands, which are skilled in executing multi-step operations.

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CISC

CISC computers have small programs. It has a huge number of compound instructions, which takes a long time to perform. Here, a single set of instruction is protected in several steps; each instruction set has additional than 300 separate instructions. Maximum instructions are finished in two to ten machine cycles. In CISC, instruction pipelining is not easily implemented.

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RISC and CISC 110

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Any Questions?

References: 1. Definitions, N. and Hope, C. (2017). What is Network Media?. [online]

Computerhope.com. Available at: https://www.computerhope.com/jargon/n/network-media.htm

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https://www.computerhope.com/jargon/n/network-media.htm



computer systems architecture - micronet international college

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