FCRTH
E1000_WRITE_REG(hw, FCRTH, 0);
E1000_WRITE_REG(hw, FCRTH, hw->fc_high_water);
E1000_WRITE_REG(hw, FCRTH, hw->fc_high_water);
sc->hw.fc.high_water = FCRTH;
IXGB_WRITE_REG(hw, FCRTH, 0);
IXGB_WRITE_REG(hw, FCRTH, hw->fc.high_water);