Computer Structure
Processor & Buses
We learned about the parts of the processor and the wires (buses) used to connect them to memory in N5.
Click the button for a recap.
Fetch Execute Cycle
The fetch-execute cycle describes the process of moving a program instruction from the computer's memory to the processor, decoding and then executing it.
The processor sets up the address bus with the required address
The processor activates the read line on the control bus
An instruction is fetched from the memory location using the data bus and stored in the instruction register
The instruction in the instruction register is decoded and executed
Performance
There are a number of factors which can affect the performance of a computer system:
Number of Processor Cores
A multi-core processor is a processor with two or more separate processing units (cores).
Each core contains an ALU, control unit and registers.
The cores can process tasks in parallel.
The greater the number of cores on a processor, the greater the number of instructions that can be carried out simultaneously.
Whilst increasing the number of cores will greatly improve system performance, it is not always possible for tasks to be shared equally between cores.
Width of the data bus
The data bus is a set of wires that transport data between the processor and main memory.
Each cycle of the fetch-execute cycle requires data to be moved along the data bus.
Increasing the width of the data bus increases the amount of data / program instructions that can be transported in a single cycle.
For example, a 64-bit data bus can carry four times as much data in a single fetch-execute cycle as a 16-bit data bus.
Cache Memory
Small amount of computer memory that provides high-speed data access to the processor.
Stores frequently used computer program instructions and data.
Typically integrated onto the motherboard or embedded in the processor.
Clock Speed
The speed at which the processor executes each instruction.
The higher the clock speed, the faster the computer can execute each instruction.
Different manufacturers use different ways to measure the clock speed, so making a comparison can be difficult.