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WAR HAZARDS

EXAMPLE 

  MULF R0, R0, R2  
  SD   R0, 0(R11)  (Store R0)
  MULF R0, R4, R6  
  SD   R0, 8(R11)  (Store R0)
  • Note that there is no data dependence between the MULF instructions, but there is a WAR hazard (``anti-dependence'') between the first SD and the second MULF.

  • With the scoreboard scheme this results in a stall

  • With Tomasulo's scheme it does not.

WHY?