OCR GCSE Computer Science: CPU Architecture, Performance, and Embedded Systems

Vocabulary practice flashcards covering CPU components, Von Neumann architecture, the fetch-execute cycle, CPU performance factors, and embedded systems based on OCR GCSE Computer Science (J277) topic notes.

Central Processing Unit (CPU)

The most important component in any computer system, attached to the motherboard, whose purpose is to process data and instructions by constantly repeating the fetch-execute cycle.

Control Unit (CU)

A CPU component that sends signals to control hardware, coordinates the flow of data inside the CPU and across the computer, and decodes instructions as part of the fetch-execute cycle.

Arithmetic Logic Unit (ALU)

A CPU component that performs mathematical calculations, logical operations, and binary shifts, storing the results of calculations in the accumulator.

Register

A small, temporary storage space within the CPU for one piece of data, instruction, or address.

Accumulator (ACC)

A register used in the execute stage that stores the results of executions and calculations made by the Arithmetic Logic Unit (ALU).

Cache Memory

Fast, temporary storage inside or very close to the CPU that stores frequently accessed data and instructions to reduce the need to repeatedly fetch them from slower RAM.

Computer Architecture

The way a computer is designed and structured.

Von Neumann Architecture

A computer architecture named after mathematician John Von Neumann that stores both program instructions and data in the same memory (RAM) and contains a control unit, ALU, registers, and cache memory.

Opcode

The technical term for an instruction, representing an action to perform (such as 'ADD' in the command 'ADD 43').

Operand

The technical term for data, representing the value to be used by an instruction (such as '43' in the command 'ADD 43').

Fetch Stage

The stage of the fetch-execute cycle where instructions are fetched from RAM and transferred into the registers inside the CPU, specifically being stored in the Memory Data Register (MDR).

Execute Stage

The stage of the fetch-execute cycle where instructions are decoded by the control unit and executed (run), with any mathematical calculations performed by the ALU and stored in the accumulator.

Program Counter (PC)

A register that stores the address of the next instruction to be fetched from RAM, which is copied into the MAR and then incremented by $1$.

Memory Address Register (MAR)

A register that stores the address of the current instruction or memory location to be fetched from RAM, once it has been copied from the PC.

Memory Data Register (MDR)

A register that stores the instruction or data fetched from the memory location identified by the MAR.

Clock Speed

The number of regular electrical pulses the CPU receives per second from the computer's clock, measured in gigahertz (GHz).

Gigahertz (GHz)

The unit used to measure clock speed, representing billions of pulses per second (for example, $3.5\text{ GHz}$ is $3.5$ billion pulses per second).

Cache Levels (L1, L2, and L3)

The three levels into which cache memory is typically split, with each level generally being larger in capacity but slower to access than the previous level.

Core

An individual processing unit within the CPU containing components such as a control unit, ALU, registers, and cache, which can independently perform the fetch-execute cycle.

Embedded System

A computer system built into a larger machine to provide a means of control by performing specific pre-programmed tasks that are often stored in ROM.