Made by El ˚₊‧꒰ა ☆ ໒꒱ ‧₊˚ - OCR GCSE Comp Sci Notes
1.1 Systems Architecture
1.1.1 Architecture of CPU
Purpose of CPU (Central Processing Unit/Microprocessor)
★ CPU is a computer system, referred to as the ‘brain’ of a computer.
★ CPU used to execute a series of instructions by using inputs and outputs repeatedly.
★ CPU processes data by fetching, decoding and executing instructions as its function.
Fetch-Decode-Execute Cycle:
★ In each cycle, an instruction is retrieved from memory (fetching), which turns into a
command (decoding), then actions as an output are carried out (executing).
Common CPU Components & Functions
● ALU (Arithmetic Logic Unit)
ᯓ★ Performs all calculations and logical operations.
ᯓ★ It also transfers data to and from registers.
ᯓ★ ALU inputs and outputs in binary when carrying out an instruction.
ᯓ★‘F-E’ Cycle - ALU stores the results of calculations.
● CU (Central Unit)
ᯓ★ CU sends data and control signals to direct the operations of the CPU.
ᯓ★ Manages data flow between various components and instructions execution.
ᯓ★ ‘F-E’ Cycle: CU retrieves instructions from memory, instructions then analysed to
be decoded in order to control what operation is performed next. Lastly, CU sends
control signals to other components to perform the instruction.
● Cache
ᯓ★ Cache memory temporarily stores data.
ᯓ★ Cache is slower than registers but faster than RAM.
ᯓ★ Swapping the CPU with one that has more cache memory, it would improve
computers performance, as cache is faster than RAM.
● Registers
ᯓ★ Small, temporary storage for data and instruction during the execution process.
─── ⋆⋅☆⋅⋆ ───
1.1 Systems Architecture
1.1.1 Architecture of CPU
Purpose of CPU (Central Processing Unit/Microprocessor)
★ CPU is a computer system, referred to as the ‘brain’ of a computer.
★ CPU used to execute a series of instructions by using inputs and outputs repeatedly.
★ CPU processes data by fetching, decoding and executing instructions as its function.
Fetch-Decode-Execute Cycle:
★ In each cycle, an instruction is retrieved from memory (fetching), which turns into a
command (decoding), then actions as an output are carried out (executing).
Common CPU Components & Functions
● ALU (Arithmetic Logic Unit)
ᯓ★ Performs all calculations and logical operations.
ᯓ★ It also transfers data to and from registers.
ᯓ★ ALU inputs and outputs in binary when carrying out an instruction.
ᯓ★‘F-E’ Cycle - ALU stores the results of calculations.
● CU (Central Unit)
ᯓ★ CU sends data and control signals to direct the operations of the CPU.
ᯓ★ Manages data flow between various components and instructions execution.
ᯓ★ ‘F-E’ Cycle: CU retrieves instructions from memory, instructions then analysed to
be decoded in order to control what operation is performed next. Lastly, CU sends
control signals to other components to perform the instruction.
● Cache
ᯓ★ Cache memory temporarily stores data.
ᯓ★ Cache is slower than registers but faster than RAM.
ᯓ★ Swapping the CPU with one that has more cache memory, it would improve
computers performance, as cache is faster than RAM.
● Registers
ᯓ★ Small, temporary storage for data and instruction during the execution process.
─── ⋆⋅☆⋅⋆ ───
