Here is the scenario, you are building your new rig and you have installed the shiny new H100i and you press the power button and you install the OS and configure it and then install all the drivers etc. (I have my own method whereby I install the OS, then I install the latest LAN driver for the board and then do all the Windows updates and only when there are no more updates do I install the rest of the motherboard and graphics cards drivers and utilities).
You now run Prime95 and your temperatures are pretty disappointing to cr@p.
So you try different fans and the performance still doesn't really improve.
You now get onto forums like this one and voice your anger and call the reviewers liars because they - compared to your results - obviously fudged the H100i tests and are in the pocket of Corsair.
The cause of your problem is trivial to solve and it is a fix that takes only a few minutes.
The solution is washers.
The mounting kit for the H100i is made for all Intel motherboards and different motherboards have different thickness of backplate. If your motherboard has a thinner backplate then you can screw down the H100i as tightly as you like, it will not make proper contact with the CPU. Thus the cooling you achieve of the CPU will be disappointing.
To rectify this, take the plastic washer off each of the four mount posts and put some extra washers in underneath then replace the original plastic washer on the top. The top of the mount should be just above the surface motherboard - now obviously you are going to have to try different thicknesses of washers until you get it right.
When you now screw in the standoffs and then attach the pump you will be able to screw it on to make a solid connection to your CPU.
This applies to all Intel motherboards except the 2011.