In an interview with Bit-tech, ASUS ROG motherboard product manager Andrew Wu has let the proverbial cat out of the bag: apparently, compatibility of Z270 boards with Coffee Lake processors wouldn’t have been impossible after all. When asked why the new Coffee Lake CPUs aren’t compatible with the previously released Z270 platform, Andrew Wu explained that it” (…) depends on Intel’s decision.” Andrew Wu also went on to mention that Intel’s stated power delivery reasons don’t “make much difference”, and that ASUS themselves could make their Z270 motherboards compatible with Coffee Lake. For that, however, they’d need “(…) an upgrade from the ME [Management Engine] and a BIOS update”, for which “Intel somehow has locked the compatibility.”
It seems all of that extra “pin-count” doesn’t really matter in the grand scheme of the current Coffee Lake lineup with up to six core processors – the CPU socket and platform as designed with Z270 would have been able to handle the increased core counts and power loads. The question gets murkier with Intel’s ability to release an 8-core CPU to the Z370 platform though – that particular amount of cores might indeed prove to be too much for Z270’s power delivery. Making an educated guess, it would seem that Intel could have allowed for Coffee Lake compatibility on Z270 motherboards on CPUs up to 6 cores, but would need the new revisions on the Z370 platform to allow for operation of 8-core Coffee Lake chips.