Compatibility of Z170 motherboards with Kaby lake processors

Question

Motherboard using Intel's Z170 chipset have been out since before the Kaby lake line of CPUs (7th generation core processors a.k.a. 7000 series) were out. In several online stores you still see them listed as supporting "6th generation" Intel core processors (6000 series). I have noticed that several forums claim that you can run Kaby lake CPUs on Z170; and others say you need a BIOS upgrade. (The socket is physically the same.)

So, which is it, among the following options:

1. Can't use Kaby lake's with Z170 boards at all
2. Always need a BIOS upgrade, which manufacturers don't pre-apply
3. Kaby lakes just run on Z170s out of the box
4. Depends on the manufacturer and/or the motherboard model (please elaborate if you can)

Answer 1

In fact Kaby Lake microarchitecture is an 'Optimiation' of Skylake, as is said by Intel. It remains the same lithography of 14nm since Broadwell with a slightly increased operatibg frequency. As has always been, processors of the same architecture family can share motherboards. For example all 6-series and all 7-series motherboards can handle both Sandy Bridge and Ivy Bridge. But when IVB initially came out, the slight difference in microinstructions requires different handling from SNB, thus demand a BIOS update. Usually new MBs manufatured have up-to-date BIOS out-of-the-box, so those assembled before a suitable BIOS for Kaby Lake are in need of a update so they can run Kaby Lake, while those assembled after KBL is out don't necessarily need to be updated before they operate properly.