Board manufacturer's have now brought out the Z
270X MOBO series, which are designed specifically to work well with the i7 Kabylake processors. The Z
170Xboards already in the sales distribution pipeline cannot run an i7-7700 with the factory BIOS on the board.
However, Gigabyte has a BIOS to download that will support the i7 on the Z
170X but the BIOS must be installed and to install it you must have a compatible
6th generation Intel CPU (i3 or i5) already installed. In other words, Gigabyte has updated their BIOS as as to make it possible for you to use an i7 but they expect most (all?) Z
170X users to be up and running already and therefore interested in updating to the i7, not in making an initial installation.
The real question is
WHY you want to use a new generation CPU on a MOBO designed for the previous generation. The old board is cheaper of course (because people buying anything new usually want this years new model, not last years new model. That's why car dealers (and MOBO dealers) discount the old models.
Performance, however is not very different for the two processors on the Z
170X board. If you were going with a newer Z
270X MOBO, there might be some performance advantage, depending on your needs.
By the way, this is what the opening note to the
April buyer's guide says:
"If you're building a CustoMac, Intel's 7th Generation Kaby Lake CPUs and 200 Series motherboards are
now available, however the platform is not native yet in macOS. It is a great time to take advantage of closeout pricing on fully compatible components.
Intel's 6th Generation Skylake CPU + 100 Series Motherboards + NVIDIA GeForce 'Pascal' Graphics Card is [still] the current recommendation." (emphasis added)