Characteristics of the CPU Flashcards

1
Q

What is the job of the CPU?

A
  • The CPU is responsible for processing all data within the computer
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2
Q

What are the components of the CPU?

A
  • Arithmetic and logic unit (ALU)
  • Control unit (CU)
  • Registers
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3
Q

What is a register?

A
  • Temporary memory storage locations inside the CPU
  • Used for a single specific purpose
  • Faster access speed than RAM and secondary storage
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4
Q

What are the different registers?

A
  • Program counter (PC)
  • Accumulator (ACC)
  • Memory address register (MAR)
  • Memory data register (MDR)
  • Current instruction register (CIR)
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5
Q

What are the different buses and their roles?

A
  • Data bus: holds data being sent to/from the CPU and RAM
  • Address bus: hold addresses being sent to/from the CPU and RAM
  • Control bus: sends signals to determine whether the other buses are in read or write mode
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6
Q

What is the role of the arithmetic and logic unit?

A
  • Performs and arithmetic calculations or logic comparisons (using AND, OR, NOT)
  • The ALU is made up of several components
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7
Q

What is the role of the control unit?

A
  • Instructions are decoded
  • Controls the data within the CPU and how it moves around
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8
Q

What is the role of the program counter?

A
  • Stores the address in memory of the next instruction that needs to be fetched
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9
Q

What is the role of the accumulator?

A
  • Values are stored temporarily, either after they have been inputted or loaded or after being calculated in the ALU
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10
Q

What is the role of the memory address register (MAR)?

A
  • Where addresses are stored, either about where data is being sent in memory or where it is being fetched from
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11
Q

What is the role of the memory data register (MDR)?

A
  • Where data / instructions are stored, either before it is sent to memory or after being fetched
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12
Q

What is the role of the current instruction register (CIR)?

A
  • When an instruction has been fetched from memory, it is loaded here before being split into opcode and operand
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13
Q

What is the ALU made up of?

A
  • Arithmetic circuit: carries out any arithmetic calculations
  • Logic circuit: carries out operations like AND, OR, NOT
  • Registers: additional registers that can store data
  • Status flags: overflow flag (if the value is too large), zero flag
  • Buses: used to transport data around the ALU
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14
Q

What is the fetch-decode-execute (FDE) cycle?

A
  • The process the CPU goes through repeatedly to process instructions
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15
Q

What are the 3 stages of the FDE cycle?

A
  • Fetch: fetchin an instruction from memory, providing the address and receiving the instruction
  • Decode: interpreting the instruction and retrieving the required data from memory
  • Execute: the CPU carries out the required action
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16
Q

What registers are used in the fetch cycle?

A
  • The program counter is loaded with 0
  • The value from the program counter is copied to the memory address register
  • The data from the memory address register (0) is sent across the address bus and the instruction to read the data is sent across the control bus
  • The data from the location in memory (0) is sent across the data bus and stored in the memory data register
  • The program counter is incremented by 1
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17
Q

What registers are used in the decode cycle?

A
  • The data is sent from the memory data register to the current instruction register where it is split into opcode and operand
  • This is sent to the control unit to be decoded
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18
Q

Which registers are used in the execute cycle?

A
  • Which registers are used here depend on the instruction being executed
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19
Q

What are the main ways in which CPU performance can be measured?

A
  • Clock speed
  • Number of cores
  • Cache
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20
Q

What is the clock speed and how does it effect CPU performance?

A
  • The clock in the computer control operation in the CPU
  • It repeatedly changes from 0 to 1 and then back to 0. Each one of these is known as a state change
  • A state change can represent one FDE cycle, however some take more than one cycle
  • Clock speed is measured in how many state changes take place in a second (Hz)
  • If a computer has a higher clock speed, it will be able to execute more instructions per second and therefore, carry out tasks more quickly
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21
Q

What is a core and how does the number of cores effect CPU performance?

A
  • A core is a processing unit within the CPU
  • Each core runs at the same speed, therefore more cores doesn’t make the CPU faster
  • Each core can carry out its own FDE cycle. Therefore, more cores means more instructions can be executed at the same time. This is known as parallel processing
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22
Q

What is cache and how does it effect CPU performance?

A
  • Cache is part of the primary storage and is used to store frequently used data and instructions
  • It is used as it is closer to the CPU than RAM and therefore faster to retreive data from
  • The more cache there is, the more data can be stored and therefore, it speeds up the performance of the CPU
23
Q

Different levels of cache

A
  • Cache is split into 3 levels:
  • Level 1: small and fast, one for each core
  • Level 2: shared between cores, slower but larger than level 1
  • Level 3: slower and larger than level 2, sits on the motherboard unlike level 1 and 2
24
Q

What is pipelining?

A
  • Pipelining is the process of carrying out multiple instructions concurrently (at the same time)
  • Each instruction will be at a different stage of the FDE cycle
  • One instruction can be fetched, while the one before is being decoded and the one before that is being executed
25
Q

How does pipelining improve processor performance?

A
  • Pipelining reduces latency
  • The CPU is not idle when waiting for the next instruction which increases the speed of execution
26
Q

What is a branch?

A
  • In a branch, the instruction in the next location in the memory is not necessarily executed next
27
Q

What is a computer architecture?

A
  • Describes how it uses the components and instructions to make the computer function
28
Q

Von Neumann architecture

A
  • Single control unit
  • Unified memory
  • Single set of buses
  • Special registers within the CPU
  • Shared address space
29
Q

Harvard architecture

A
  • Seperate instruction and data memory
  • Seperate instruction and data buses
  • Seperated memory
  • Seperate control units
  • Used in specialized embedded systems
30
Q

How does Harvard architecture improve performance over Von Neumann architecture?

A
  • Two seperate areas of memory: one for instructions and one for data; can be accessed concurrently
  • Different sets of buses: instruction and data can be accessed concurently
  • Allows pipelining
  • Super scalar: multiple instructions can be executed at the same time
  • Out of order execution
31
Q

What is an instruction set?

A
  • A computer processor will have an instruction set which it will use to execute programs
  • An instruction set are the instructions that the computer is capable of carrying out
  • The instruction set of a computer will vary from computer to computer
32
Q

What is RISC?

A
  • Reduced Instruction Set Computer
  • Consists of a smaller instruction set with fewer instructions
  • Each instruction takes one clock cycle to execute, which makes it more suitable for pipelining
  • Compilers are more complicated so will generate more instructions
  • Has fewer addressing modes
  • Is usually used in smartphones and tablets
33
Q

What is CISC?

A
  • Complex Instruction Set Computer
  • Consists of a larger instruction set with more complex instructions
  • As the instructions are more complex, they can take more than one clock cycle to execute - not suited for pipelining
  • Has more general purpose registers
  • Instructions take up less space in memory
  • Is usually used in laptops and PCs
34
Q

Pros and cons of RISC and CISC

A
  • RISC: requires less power, costs less to manufacture, takes up more space in memory
  • CISC: requires more power, costs more to manufacture, takes up less space in memory
35
Q

What is a GPU and some key features?

A
  • A GPU is responsible for processing graphics within the computer to reduce the load on the CPU
  • CPU are general purpose processors while GPU are specifically made for handling graphics
  • GPUs are likely to have built in circuits or instructions for common tasks
  • They can perform an instruction on multiple pieces of data at the same time
  • They can be part of a dedicated graphics card or embedded onto the CPU
36
Q

What can a GPU be used for other than graphics?

A
  • 3d modelliing
  • Data modelling: GPUs can handle large datasets and complex operations
  • Financial modelling: lots of simulations can run in parallel
  • Data mining
37
Q

What are the benefits of using a GPU?

A
  • Parallel processing: GPUs can handle many tasks simultaneously
  • Speed: parallel processing speeds up tasks
  • Efficiency: can perform more calculations per unit of power compared to CPUs
38
Q

What are the benefits of multicore processors?

A
  • Speed: a task can be split into subtasks which can be executed simultaneously
  • Multitasking: allows parallel processing; each core can work on a different task
  • Improved performance
  • Background tasks: can assign the background task to one core, so the users other task isn’t slowed down
39
Q

What are the drawbacks of multicore processors?

A
  • Complex programming: it is harder to write code for parallel processing
  • Debugging difficulty: it is more difficult to debug a parallel program
  • Communication between cores: can take significant time and resources
40
Q

What are input devices?

A
  • Hardware components that allow the user to interact with the computer system
  • They allow the user to input data or commands into the system
41
Q

Examples of input devices

A
  • Keyboard
  • Mouse
  • Microphone
  • Webcam
  • Game controller
42
Q

What are output devices?

A
  • Hardware components that receive information from a computer system and present it to the user, in different forms
43
Q

Examples of output devices

A
  • Monitor
  • Printer
  • Speakers
  • Headphones
  • Projector
44
Q

What should you consider when choosing the right device?

A
  • User needs
  • User skills
  • Environment
  • Cost
45
Q

What are the three types of storages?

A
  • Magnetic
  • Optical
  • Flash
46
Q

Magnetic storage devices - description, benefits and drawbacks

A
  • Stores data by magnetising particles on a disc
  • Pros: high storage capacity, relatively low cost per gigabyte, suitable for long term storage or backup
  • Cons: slower read / write speeds compared to other types, susceptible to physical damage, moving parts can wear out over time
47
Q

Optical storage devices - description, benefits and drawbacks

A
  • Stores data using a laser to burn pits into the surface of the disc
  • Pros: durable and relatively immune to environmental changes, easy to transport, suitable for distributing software
  • Cons: lower storage capacity compared to other types, slower read/write speeds, can easily be scratched or damaged
48
Q

Flash storage devices - description, benefits and drawbacks

A
  • Stores data in flash memory cells
  • Pros: fast read/write speeds due to no moving parts, less likely to fail due to physical shock, silent operation
  • Cons: higher cost per gigabyte, flash memory cells can wear out after a certain number of write cycles
49
Q

What is virtual storage?

A
  • A model of data storage where digital data is stored across ultiple servers and locations, typically hosted by third parties
50
Q

Benefits of virtual storage

A
  • Scalability: easy to increase storage capacity based on needs
  • Accessability: data can be accessed from anywhere with an internet connection
  • Data protection: data redundancy protects against data loss due to hardware failure
  • Cost-effective: pay only for the storage needed
51
Q

Drawbacks of virtual storage

A
  • Dependence on internet connection: access to data can be slow or impossible
  • Security concerns: storing sensitive data off-site can pose a risk
  • Ongoing costs: not a one time payment, costs can build up over time
52
Q

Characteristics of RAM

A
  • Random Access Memory
  • Stores data that is currently being used by the computer, such as open applications and files
  • The data in RAM can be read from and written to by the processor, allowing for fast data access and manipulation
  • RAM is volatile
  • It is directly accessible: the CPU cna access any part equally as fast
53
Q

Characteristics of ROM

A
  • Read Only Memory
  • Stores the BIOS or firmware that is used to start up the computer
  • The data needs to be preserved even when the computer is turned off
  • ROM is non-volatile