Computer Organisation and Architecture

Question 1

What is the ALU?

Answer 1

• Arithmetic Logic Unit
• Performs Arithmetic and Logical Operations
• Arithmetic like Addition
• Logical like AND, OR, XOR

Question 2

What is the Control Unit?

Answer 2

• A processor’s control unit is responsible of controlling the various components of the processor.
  *It is responsible for controlling FEC.

Question 3

What is the Clock?

Answer 3

• Inside a computer’s processor is the system clock, a device that generates a timing signal which changes at a regular frequency. * This signal is used to synchronise communication between the components of the processor and the rest of the computer system.

Question 4

What is the Program Counter?

Answer 4

• Used to hold the memory address of the next instruction to be executed in the FEC

Question 5

What is the CIR?

Answer 5

• Current Instruction Register
• Holds the instruction that is currently being executed by the processor

Question 6

What is the MAR?

Answer 6

• Memory Address Register
• Stores the memory address of a memory location that is to be read form or written to.

Question 7

What is the MDR/MBR?

Answer 7

• Memory Data Register/Memory Buffer Register
• Holds the contents of a memory location that has been read from or data that is to be stored.

Question 8

What is the Status Register?

Answer 8

Contains a number of bits, the values of which can change to indicate the occurrence of an interrupt.

Question 9

What is a Processor?

Answer 9

• Responds to and processes the instructions that drive the computer
• Contains:
  * Control Unit (CU)
  * Arithmetic Logic Unit (ALU)
  * Registers

Question 10

What is a Register?

Answer 10

• A small, high-speed memory/storage locations within a computer’s CPU.

Question 11

What is a Bus?

Answer 11

• A bus is a set of parallel wires connecting two or more components of a computer.
• They can be:
  * Data Bus
  * Control Bus
  * Address Bus

Question 12

What is a Control Bus?

Answer 12

• Bi-Directional
• Purpose is to transmit command, timing and specific status information between components.
• Control Line example:
  
  • Memory Write
  • Interrupt Request
  • Bus Grant
  • Memory Read

Question 13

What is a Address Bus?

Answer 13

• Memory divided up internally into units called <b> words </b>
• Each word in memory has its own specific address
• When processor wishes to read a word of data from memory, it first puts the address of that word on the address bus
• The width of the address bus determines the maximum possible memory capacity of the system.
• For example: If the address bus had only 8 lines, then the max address it could transmit would be 1111 1111. or 255.
  
  • Max capacity of 256, including address 0.

Question 14

What is a Data Bus?

Answer 14

• Data Bus typically consists of 8, 16, 32, 64 separate lines.
• Bi-Directional path for moving data and instructions between components.
• Width of the data bus is key factors in determining overall performance.
• For example: if data bus is 8 bits wide and each instruction is 16 bits long, then the processor must access main memory twice just to fetch the instruction.