Z370 increments by 100
New Intel CPUs generally mean new motherboards every couple generations or so, and Coffee Lake is no different. These CPUs will still drop into an LGA 1151 socket, but don't be fooled—it's not the same as the LGA 1151 we know from Z170 and Z270 boards. Intel's official statements on this platform change vaguely cite the need for improved power delivery to support six cores, but we found that position confusing given the already-overbuilt power delivery circuitry on many enthusiast Z270 boards.
Thankfully, the enterprising David Schor of WikiChip has ferreted out exactly what's changed in the Z370 version, and the answer appears to be more power-delivery and ground pins taken at least in part from a group that were previously reserved. Note to Intel: "we changed the pinout" was all you had to say without giving anything more away.
Even with the different pinout and lack of support for older CPUs, Z370 motherboards still use the LGA 1151 name. I suppose this is technically correct, but continuity implies compatibility, and I expect some builders will be surprised when they learn that Z370 boards can't be used with physcially-compatible older CPUs. Intel says it'll avoid confusion among buyers by putting "Supports eighth-generation Intel processors" on motherboard boxes, and early packaging renders suggest "Requires Intel 300 series-based chipset motherboard" will be on at least one side of the box in somewhat-prominent text.
We still don't think that does nearly enough to avoid befuddlement, however. Buyers will still see "LGA 1151" on both CPU boxes and motherboard boxes, and Z270 supported both sixth- and seventh-gen Intel processors without complaint, so some will inevitably assume one can mix and match all of these things freely. Call the socket LGA 1151 v2, call it LGA 1151+, we don't care—just call it something different. Newegg seems to have settled on the term "LGA 1151 (300 Series)," and that's a good enough start.
You can put a sixth- or seventh-gen LGA 1151 CPU into a Z370 motherboard, and it will drop in and latch just fine. I tried as much with a Core i5-7600K, and it didn't harm anything even after I tried to power it up. Z370 boards will not even POST with these older chips installed, however, and I wasn't brave enough to risk anything by putting our i7-8700K in a Z270 board to find out what would happen.
Beyond the electrical changes in the socket, the Z370 PCH itself offers the exact same resources as Z270 before it. Motherboard makers can tap 24 flex I/O lanes for use as PCIe 3.0 slots, SATA ports, M.2 slots, and more. Up to 10 USB 3.0 ports and up to 14 USB 2.0 ports can also be called upon for peripheral connectivity. Six SATA ports round out the package. Intel advertises Thunderbolt and Optane support from Z370, as well, just as it did with Z270.
The lack of new features in Z370 is honestly a bit underwhelming. Z270 was already the basis for some fine motherboards, and I never found myself wanting much of anything from them for peripheral I/O. Still, given that the life of a system is often five years or more these days, it's annoying that Z370 itself offers no new features, connectivity, or quality-of-life improvements compared to its outgoing counterpart.
AMD's X370 and B350 chipsets each offer two native USB 3.1 Gen 2 controllers for motherboard makers to tap, and Ryzen 3, 5, and 7 CPUs can devote four lanes of CPU-connected PCIe to M.2 slots in addition to the 16 available for graphics cards or other expansion cards. That dedicated x4 link for storage devices is especially nice given the lane-sharing circus that can ensue if builders try to use every port available from modern Intel boards.