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I2O2

Pipeline Structure

Pasted image 20221021062200.png

Similar to I4, but ditches the constant pipeline length.

Scoreboard

Uses scoreboard in the same way as I4, but also uses it to track structural hazards on the writeback port.

Pipeline Diagram

0 MUL R1, R2, R3    F  D  I  Y0 Y1 Y2 Y3 W 
1 ADDIU R11, R10, 1    F  D  I  X0 W 
2 MUL R5, R1, R4          F  D  I  I  I  Y0 Y1 Y2 Y3 W 
3 MUL R7, R5, R6             F  D  D  D  I  I  I  I  Y0 Y1 Y2 Y3 W 
4 ADDIU R12,R11,1               F  F  F  D  D  D  D  I  X0 W 
5 ADDIU R13,R12,1                        F  F  F  F  D  I  X0 W 
6 ADDIU R14,R12,2                                    F  D  I  I X0 W
  • Stalling is done on the issue stage to avoid structural hazard on writeback