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
2
Q
What are the components of the CPU?
A
- Arithmetic and logic unit (ALU)
- Control unit (CU)
- Registers
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
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)
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
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
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
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
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
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
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
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
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
14
Q
What is the fetch-decode-execute (FDE) cycle?
A
- The process the CPU goes through repeatedly to process instructions
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
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
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
18
Q
Which registers are used in the execute cycle?
A
- Which registers are used here depend on the instruction being executed
19
Q
What are the main ways in which CPU performance can be measured?
A
- Clock speed
- Number of cores
- Cache
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
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
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
How does pipelining improve processor performance?
- Pipelining reduces latency
- The CPU is not idle when waiting for the next instruction which increases the speed of execution
26
What is a branch?
- In a branch, the instruction in the next location in the memory is not necessarily executed next
27
What is a computer architecture?
- Describes how it uses the components and instructions to make the computer function
28
Von Neumann architecture
- Single control unit
- Unified memory
- Single set of buses
- Special registers within the CPU
- Shared address space
29
Harvard architecture
- Seperate instruction and data memory
- Seperate instruction and data buses
- Seperated memory
- Seperate control units
- Used in specialized embedded systems
30
How does Harvard architecture improve performance over Von Neumann architecture?
- 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
What is an instruction set?
- 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
What is RISC?
- 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
What is CISC?
- 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
Pros and cons of RISC and CISC
- 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
What is a GPU and some key features?
- 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
What can a GPU be used for other than graphics?
- 3d modelliing
- Data modelling: GPUs can handle large datasets and complex operations
- Financial modelling: lots of simulations can run in parallel
- Data mining
37
What are the benefits of using a GPU?
- 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
What are the benefits of multicore processors?
- 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
What are the drawbacks of multicore processors?
- 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
What are input devices?
- 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
Examples of input devices
- Keyboard
- Mouse
- Microphone
- Webcam
- Game controller
42
What are output devices?
- Hardware components that receive information from a computer system and present it to the user, in different forms
43
Examples of output devices
- Monitor
- Printer
- Speakers
- Headphones
- Projector
44
What should you consider when choosing the right device?
- User needs
- User skills
- Environment
- Cost
45
What are the three types of storages?
- Magnetic
- Optical
- Flash
46
Magnetic storage devices - description, benefits and drawbacks
- 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
Optical storage devices - description, benefits and drawbacks
- 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
Flash storage devices - description, benefits and drawbacks
- 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
What is virtual storage?
- A model of data storage where digital data is stored across ultiple servers and locations, typically hosted by third parties
50
Benefits of virtual storage
- 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
Drawbacks of virtual storage
- 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
Characteristics of RAM
- 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
Characteristics of ROM
- 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
