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Chapter one Computer Science
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- 1How does the CPU work? (two points)-has a number of components which enable it to carry out its task
-work by continually fetching instructions from memory, decoding them and executing them - 2What is the purpose of the Control Unit?Controls and Coordinates the activities of the CPU, directing the flow of data between the CPU and other devices
- 3What is the definition of a bus?A set of parallel wires connecting two or more components of a computer
Addresses can only travel one way on the address bus - 4How does the CPU access main memory?It sends the address to memory on the address bus
- 5What is the purpose of the control bus?Transmits commands, timing and specific status info between system components
Bi-directional - 6What is the purpose of the data bus?Provides a single path for moving data and instructions between system components
- 7What is the purpose of the address bus?Transmits words addresses that are used as operands in program instructions so that the data can be retrieved and sent back to the processor
- 8What is a word?A fixed group of six digits which is handled as a unit by the processor
- 9What are examples of control lines?- Bus request = indicates that a device is requesting use of the data bus
-Bus grant = indicates that the CPU has granted access to data bus
-Memory write = causes data on data bus to be written into the addressed location
-Interrupt request = indicates that a device is requesting access to the CPU
-Clock = used to synchronise operations - 10What does the ALU do?Arithmetic Logic Unit
Perform arithmetic and logical operations on data
AND, OR, XOR, NOT - 11What is a register?Special memory cells that operate at very high speeds
- 12What does the program counter do?Holds the addresses of the next instruction to be executed, or the next in a sequence
- 13What does the current instruction register do?Holds the current instruction to be carried out, divided into operand and opcode
- 14What does the memory address register do?Holds the address of memory location from which data is to be fetched or to which data is written.
- 15What does the memory data register do?Used to temporarily store data read from or written to memory
- 16What happens at the fetch point of the cycle?1) Address of the next instruction is copied from the program counter to the MAR
2) Instruction held at the address is copied to the MDR
3) Content of the program counter is incremented so that it holds the address of the next instruction - 17What happens at the decode point of the cycle?1) The instruction in the CIR is decoded
2) Instruction is split into operand and opcode and the opcode is used to determine the type of instruction and what hardware to use to execute it - 18What happens at the execute point of the cycle?1) The appropriate instruction/opcode is carried out on the operand
- 19What are the main three factors that effect performance of the CPU?1) clock speed
2) number of cores linked together on a single chip
3) the amount and type of cache memory - 20How does clock speed effect performance?A faster clock speed means instructions are executed faster.
System clock generates signals (1 and 0) read in binary. All processor activities begin on a clock pulse, and may take longer than one clock cycle to complete - 21How does Number of Cores effect performance? How many do modern computers have?More cores = faster performance
Modern computers have multiple cores - 22What is cache and how is it used?Cache is a small amount of expensive, very fast memory in the CPU
When an instruction is being fetched it is copied to the cache so if it is needed it again it can be accessed faster than going back to the main memory. - 23What are the different levels of cache?Level one = extremely fast but small, between 2-64 kb
Level two = fairly fast and medium sized, 256kb to 2mb
Some computers also have level three cache - 24What is pipelining?Pipelining is a technique used by some processors to improve performance.
The next instruction is fetched as the processor is completing the current instruction.
Common in microprocessors in personal computers
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- Fichas sobre Chapter one Computer Science, creado por Sophie Aldous el 05/01/2018.
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