The Simple Datapath By Mau Huey Ching

To execute one instruction in one clock cycle

• No data path resource can be used more than once per instruction. Any element needed more than once must be duplicated.
  • One data memory
  • One instruction memory

The branch operation requires

• Register file: for the two operands, the same as the RF for arithmetic-logic and load-store operations.
• ALU: to compare the two operands, the same as the ALU for the arithmetic-logic and load-store operations. The zero status signal indicates whether or not the two operands are equal.
• Sign-extension unit: the same as the unit for the load-store operations.
• Shifter: shift left by 2 bits. The input and output are all 32 bits.

ALU

• Inputs/outputs
  • Two 32-bit inputs
  • one 32-bit output
  • 3-bit ALU operation

Data Memory

Consider the MIPS load word and store word instructions:

  lw    $t1, offset($t2)
  sw    $t1, offset($t2)

Data memory

• Address
• Data input (32 bits)  
• Write enable
• Read enable