WAW Hazards
Instruction i writes f-p register Fx at time t
Instruction i + k writes f-p register Fx at time t - m
But no instruction i + 1, i +2, i+k uses Fx (otherwise there would be a stall)
Only requirement is that i + k ‘s result be stored
Solutions:
- Squash i : difficult to know where it is in the pipe
- At ID stage check that result register is not a result register in all
subsequent stages of other units. If it is, stall appropriate number of cycles.