1.1.1 Structure of a Processor

What does the Arithmetic and Logic unit do?

• completes all the arithmetical and logical operations.
• holds the address of the next instruction.
• Holds the address of a location that is to be read from or written to.
• Temporarily stores the data that has just been read from or the data needs to be written.

What is the Control Unit?

• A part of the processor which directs operations inside the CPU.
• Small memory cells that operate at high speeds
• holds the address of the next instruction.
• Holds the address of a location that is to be read from or written to.
• Temporarily stores the data that has just been read from or the data needs to be written.

What are registers?

• Small memory cells that operate at high speeds
• A part of the processor which directs operations inside the CPU.
• holds the address of the next instruction.
• Holds the address of a location that is to be read from or written to.
• Temporarily stores the data that has just been read from or the data needs to be written.

What does the Program Counter (PC) do?

• holds the address of the next instruction.
• Holds the address of a location that is to be read from or written to.
• Temporarily stores the data that has just been read from or the data needs to be written.
• Small memory cells that operate at high speeds
• A part of the processor which directs operations inside the CPU.

What does the Memory Address Register do?

• Holds the address of a location that is to be read from or written to.
• Temporarily stores the data that has just been read from or the data needs to be written.
• Small memory cells that operate at high speeds
• A part of the processor which directs operations inside the CPU.
• holds the address of the next instruction.

What does the Memory Data Register do?

• Temporarily stores the data that has just been read from or the data needs to be written.
• Small memory cells that operate at high speeds
• A part of the processor which directs operations inside the CPU.
• holds the address of the next instruction.
• Holds the address of a location that is to be read from or written to.

What occurs during the fetch phase?

• The address from the PC is copied to the MAR,
• Instruction held at that address is copied to the MDR by the data bus, simultaneously the contents of the PC is increased by 1,
• The value of the MDR is copied to the CIR
• The contents of the CIR is split into operand and opcode.
• The opcode is executed on the data.

What is the clock speed?

• The number of clock cycles completed per second.
• the CPU’s onboard memory which can be accessed a lot faster than main memory
• The process of completing the fetch, decode and execute of three separate files simultaneously
• It is used to synchronise instructions.

What is cache memory?

• the CPU’s onboard memory which can be accessed a lot faster than main memory
• The number of clock cycles completed per second.
• The process of completing the fetch, decode and execute of three separate files simultaneously
• It is used to synchronise instructions.

What is the role of the PC?

• Stores the results of calculations made by the ALU

• Stores the most recently fetched instruction that is waiting to be decoded and executed

• Stores the data that has been fetched from or stored in memory

• Keeps track of the memory location of the line of machine code being executed. It changes to point to the next instruction needed for the FDE cycle allowing the program to be executed in sequence

• Stores the address of the data or instructions that are to be fetched from or sent to