It took some time and a whole lot of tweaking, but modders have finally figured out a way to get Intel's Coffee Lake processors running on older motherboards based on Intel's Z270 and Z170 chipsets.
That was not supposed to happen. Even though Coffee Lake is pin compatible with older LGA 1151 motherboards, the official word from Intel is that the power requirements differ, and as such Coffee Lake only works in newer motherboards based on Intel's Z370 chipset.
To what extent the incompatibility between Coffee Lake and Z270/Z170 motherboards exists is not entirely clear. Andrew Wu, product manager for Republic of Gamers (ROG) motherboards at Asus, told Bit-Tech in October that it was "Intel's decision" not to support Coffee Lake on older boards. He also downplayed the power requirements, saying it only "makes a little bit of difference, but not much."
As far as Wu was concerned when he made those comments, getting Coffee Lake to run on older motherboards would be possible with "an upgrade from the ME [Management Engine] and a BIOS update."
Since then, there have been attempts to get Coffee Lake CPUs to run in Z270 and Z170 motherboards with limited success. Now, however, there is a forum post on Overclock.net that outlines how it can be done.
It is a fairly involved process and specific to ASRock motherboards, which the modders claim "have proven to work well" with the steps that are outlined.
"A socketed BIOS chip is desirable as it could reduce the risk of bricking the board. Because of higher power limits I would not suggest this mod with i5 and i7 K series CPUs," one of the modders wrote.
In short, getting a Coffee Lake processor to run in an older motherboard requires making tweaks to the CPU's microcode, the iGPU's UEFI GOP driver, and some Management Engine bootstraps.
The modders were able to get a Core i3-8300 processor to boot in a couple of older boards, but not a Core i7-8700 chip. That is a higher core chip, of course—six cores instead of four—which seems to suggest that the power issue is related to driving higher core counts.
We have not tinkered with this mod ourselves, but for anyone interested, you can find more information here. Just be warned that you could end up with bricked hardware, so obviously proceed with caution.