i5-7600k on a MSI Z170A PC MATE?

Solution
You can't update the BIOS if you can't boot with that i5-7600K. You need 6th-gen to boot the Z170 and update its BIOS so that your i5-7600K can be used.

Now, there is a ***chance*** that the MSI Z170A PC MATE you will get ***might*** have an updated BIOS already out-of-the-box ***IF*** it was made after the release of the 7th-gen Kaby Lake. There's also a **chance ** it might not.

So, to eliminate these incompatibilities/issues, I'd highly suggest you get a Z270 motherboard instead.

MSI Z270 PC MATE ATX LGA1151 Motherboard ($124.99 @ B&H)
You can't update the BIOS if you can't boot with that i5-7600K. You need 6th-gen to boot the Z170 and update its BIOS so that your i5-7600K can be used.

Now, there is a ***chance*** that the MSI Z170A PC MATE you will get ***might*** have an updated BIOS already out-of-the-box ***IF*** it was made after the release of the 7th-gen Kaby Lake. There's also a **chance ** it might not.

So, to eliminate these incompatibilities/issues, I'd highly suggest you get a Z270 motherboard instead.

MSI Z270 PC MATE ATX LGA1151 Motherboard ($124.99 @ B&H)
 
Solution