3.1 Computer architecture

By the end of this section you should be able to

• 3.1.1 Describe the role of the CPU and a microprocessor
• 3.1.2 Describe the components of a Von Neumann CPU
• 3.1.3 Describe the fetch–decode–execute cycle
• 3.1.4 Explain how cores, cache and clock speed affect performance
• 3.1.5 Explain what an instruction set is
• 3.1.6 Describe embedded systems and where they are used

Lessons

1. Von Neumann and the FDE cycle
2. Inside the CPU
3. Buses
4. Cores and clock speed
5. Cache
6. Instruction sets
7. Embedded systems

Key vocabulary

Central processing unit (CPU)

Processes instructions and data so that results can be output.

Arithmetic logic unit (ALU)

Carries out calculations and logical comparisons.

Control unit (CU)

Sends control signals to manage the fetch–decode–execute cycle.

Program counter (PC)

Holds the address of the next instruction to be fetched.

Memory address register (MAR)

Holds the address of the memory location being read from or written to.

Memory data register (MDR)

Holds the data or instruction just fetched from, or about to be written to, memory.

Accumulator (ACC)

Holds the result of calculations carried out by the ALU.

Cache

Small, fast memory in the CPU that stores frequently used instructions and data.

Instruction set

The list of all the machine code commands a CPU can process.

Embedded system

A computer system built into a device to perform a dedicated function.