I don' know why but i have 2 GPU who won't go in "boost" mod, look at the pic:
that gpu is under in term of gpu clock...
this one is ok.
someone have an idea ? i'm missing like 10-15% of performance for the GPU...
edit: these gpu who won't boost seem to be hotter than the others GPUs, don't know why but they have 5°c more than the other