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 times.