The governor on the chip will only allow a multiplier of 38 on every core at the same time. A single core can have a multiplier of 40, but the other cores will not have this multiplier and/or they will be in a halt state.
Bclk has nothing to do with the multiplier the chip will allow. But yes, it's 3.8 at 100 bclk and ~4.0 at 105.
If you do not touch the Bclk, the max you will see is 3.8GHz on all cores.