Thuc notes - CPU Register

• It’s high-speed memory storage used by the processor.
• It’s used support for the processor to store, decode and execute computer instruction.
• It’s the fastest memory level in computer architect

Memory register types:

• Accumulator (Arithmetic Logical Unit)
  • Performing arithmetic operations and also in logical operations
  • Holds the initial data, intermediate results and final result of the instruction
• Flag Register
• Memory Data Register
  • Store data to be written into or to be read out from the addressed location.
• Program Counter
  • Is called “instruction pointer”.
  • Store address of next instructions need to fetch or execute.
• Instruction Register
  • Store instruction that’s fetched from memory. Unit control will use it to decode and execute
• Stack Control Register
• Memory Buffer Register
• Index register
• Memory address register
  • Store address of memory unit

Fetch execute cycle:

• Basic operation of a computer to fetch instruction from memory and execute them.
• Steps:
  • PC (program counter) contains the address of the memory location that has the next instruction.
  • Memory’s address to copy to MAR (memory address register) through address BUS
  • Instruction content at memory’s address that’s stored in MAR is copied into MDR (memory data register)
  • Instruction content in MDR is copied to CIR (current instruction register) through data BUS
  • PC (Program counter) increase value to be ready for the next instructions
  • CPU decodes instruction content that’s stored in CIR
  • CPU executes the decoded instruction
  • CPU sends a signal to other components of the computer through control buses
  • Continue next instruction by repeating the cycle