Computer Organizations

Computer Architecture

CPU architecture

Control Unit (CU)

Program Counter (PC)

Stores the address of the next instruction

Memory Address Register (MAR)

Stores the current address

Memory Data Register (MDR)

Two way register that stores the instruction or data where MAR is pointing to.

Current Instruction Register (CIR)

Register that stores the current instruction

Arithmetic Logic Unit (ALU)

Cache

Primary Memory

Static RAM (SRAM)

SRAM are volatile semiconductor memory that uses flip flops to store each bit of data. This is characterized by fast access times and used in cache memory.

Dynamic RAM (DRAM)

DRAM are volatile memory that store each bit as a electric charge in a capacitor within each memory cell. This is characterized by denser and cheaper than SRAM, used in main system memory (RAM modules).

Machine Instruction Cycle

• Fetch
  • The next address in PC is copied to MAR
  • PC increment to point to the next instruction
  • Instruction at memory location stored in MAR is copied to MDR
  • Instruction in MDR copied to CIR
• Decode
  • CU decodes the instruction in CIR
• Execute
  • CU send the signal to relevant component of the CPU
    • Arithmetic or logical operations: ALU
    • Jump commands: Store the jump address to PC