Computer Science - Components of a computer

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  • Created by: Zaidek
  • Created on: 05-04-19 10:14
What are the Four Components of the CPU?
-Control Unit, ALU, Busses and Registers
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What is the Function of the Control Unit?
The Control unit controls and coordinates the Activities of the CPU. It directed the flow of data between the CPU and other devices. Performs the Fetch-Decode-Execute Cycle
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Name the Three Main Busses.
Address Bus, Data bus and Control Bus.
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What is a bus?
A set of parallel wires connected two or more components of a computer.
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What is Meant by the term bi-directional Bus?
Signals can be carried in both directions.
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What is the Purpose of the Control bus?
To transmit command, timing and status infomation between system components.
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Name 3 Control Lines
(3 of the 6) Bus Request, Bus Grant, Memory Write, Memory Read, Interupt Request, Clock.
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What is the use of control lines?
To handle requests between components, the data bus, adress bus and the CPU.
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What is the Data Bus?
Providing a bi-directional path for moving data and Instructions between system components.
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What is the Address bus?
Memory Devided up into words. The adress bus transmits the memory adress
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What is a Word?
A fixed size group of digits which is handled as a unit by the processor.
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Purpose of the ALU
The Arithmetic Logic Unit (ALU) performs arthimetic and logical operations on data. Performing operations such as, ADD, Subtract, Multiply etc. Or Logical operations such as: AND, OR, NOT etc...
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What are Registers?
Special memory cells tht operate at very high speed.
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What is stored in Registers?
Results of all arithmetic, logical or shift operations.
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Name the component which acts as a single register in the ALU?
The Accumulator.
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Name Four other Multi-Purpose Registers.
Program Counter, Current Instruction Register (CIR), Memory Address Register (MAR), Memory Data Register (MDR)
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What is the purpose of the Program Counter?
Holding the address of the next instruction to be executed. The address is copied from the CIR to the Program Counter.
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What is the Purpose of the Current Instruction Register (CIR)?
Holds the Current Instruction being executed. divided into Operand and Opcode.
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What is the Purpose of the Memory Address Register (MAR)?
Holds the Address of the memory location from which data/Instruction is to be fetched or written from.
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What is the Purpose of the Memory Data Register (MDR)?
Used to temporarily store the data read or written to memory. Also known as the Memory Buffer Register.
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How are Registers Used in the Fetch Phase?
Address of next instruction is copied from Program Counter to Memory adress register. Instruction held at address is copied to memory data register and program counter is incremented. Contents of the MDR are copied to the CIR.
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How are Registers Used in the Decode Phase?
Instruction in CIR is decoded. The opcode and Operand is then copied to either: MAR, MDR or ALU, depending on contents of the operand.
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What Main factors affect processor performance?
Clock speed, Number of Cores, Ammount and type of Cache Memory.
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What is Clock Speed?
The System Clock that generates a series of signals, switching between 1s and 0s several million times a second, synchronising CPU operations. CPU starts a new operation every clock cycle.
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How does Clock speed Increase Processor Performance?
The Greater the clock speed of a processor, the faster instructions will be executed, allowing for more instructions to be performed, increasing the performance of the Processor.
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What are Cores?
Multiple processors linked together in the same integrated ciruit.
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How do cores improve Processor Performance?
Process multiple instructions at the same time, making the processor 2, 3 or more times faster
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What is Cache Memory?
Small Amount of expensive, very fast memory inside the CPU. When an instruction is fetched from memory is it copied into the cache so if it is needed again soon after, it can be fetched from cache.
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Name Some features of the Von Neumann Architecture.
Data and programs share the same memory. One bus used to transfer data and instructions. Programs optimised in size.
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Name some features of the Harvard Architecture.
Instructions and data are held in separate memory. Parallel data and instruction busses used. Programs tend to be large.
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What is an embedded system?
Special Purpose computers built into devices often operating in real time. E.G - GPS, Traffic lights etc.
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What are the Two Instruction set Architectures?
Complex Instruction Set Computers (CISC) and Reduced Instruction Set Computers (RISC)
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Name some Features of CISC Architecture.
Used to complete tasks with a few lines of assembly code. Can have more clock cycles. Can do more complex instructions such as MULT(A, B) etc. The Compiler has little work to do to translate. However many extra unused instructions get inbuilt.
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Name some Features of RISC Architectures.
Only Simple Instructions, each taking one clock cycle. Has to do more work and time to translate high level code into machine code. More Ram is Used. Due to the one clock cycle per instruction, it still is fast. Replaced CISC as a processor design.
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What are Co-processors.
An extra processor used to supplement the functions of the primary processor. It may be used to perform floating point arithmetic, graphics processing and other functions. Cant do as much as a general purpose processor, only carries limited functions
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Name some examples of Input Devices.
Bar codes / Bar code readers, Pen type readers, laser scanners, camera based readers.
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What is Radio Frequency Identification (RFID)?
A device that uses both input and output. An Input Device to read signals from an RFID chip, and transmit a signal from an active tag. Used in shopping, bank cards etc.
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What is the difference between active and passive tags?
Active tags are larger and include a battery to power the chip. they can pick up signals from much father away. Mostly used in cars etc. Passive tags are cheaper to produce and do not have a battery. They have a much shorter transmit distance 1m.
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Name some examples of Output Devices.
Screens, Printers, Projectors, Speakers etc.
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What is the difference between the three types of printers?
Laser Printers - high quality, high speed printing, uses powdered ink. Inkjet - Work by spraying minute dots onto the paper to create an image. Dot Matrix - Also know as Impact Printers. The print head has a matrix of pins used to strike the paper.
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What is the difference between LCD and OLED Screens?
Liquid Crystal Display (LDC) monitors contain groups of red, green and blue diodes to form each pixel. consume little power. Organic LED (OLED) screens are thinner lighter and brighter. Screen is plastic rather than glass. Longer Battery life.
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Why is secondary storage needed?
As it retains its contents when switched off. Allowing for permanent memory storage
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Name the different Secondary Storage Devices.
Hard disk, Optical Disk, Solid-state Disk.
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How do Hard Disks work?
Uses rigid rotating platters coated in magnetic material. The Disk is divided into tracks in concentric circles. The Disk spins fast (up to 10000 RPM). Read / write head used to read and write from it (Like an old record player).
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Name the Advantages and Disadvantages of Hard Disks.
Advantages - Huge storage capacity (640GB) , smaller and denser. Disadvantages - less portable, not very durable due to moving parts.
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What are the three Optical Disk Formats?
CD-ROM (Read Only), CD-R (Record-able) , CD-RW (Re-writable)
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How does an optical Disk Work?
Using a high powered laser to "burn" sections of its surface making them less reflective
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How much space can Optical disks hold?
Cd-ROMs hold about 700 Mb of data. Blue rays can hold up[ to 50Gb.
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Name the Advantages and Disadvantages of Optical Disks.
Advantages - Cheap to produce, very portable. Disadvantages - Can become corrupted or damaged easily (not very durable).
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How do Solid-state Disks Work?
Using arrays of chips arranged on a board. These work as the storage for the memory / data.
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What are the Advantages and Disadvantages of Solid State?
Advantages - Fast access speed, Consume less power, portable and durable (Due to no moving parts). Disadvantages - Relatively small storage space.
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What is stored in ROM?
Holds information that needed to be permanently in memory. The Bootstrap loader and software in embedded systems are all held in ROM.
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