Expansion and storage options
Unlike some higher-end boards bristling with M.2 slots, U.2 connectors, and vestigial SATA Express ports, the Z270E's connectivity and expansion options are straightforward. Asus provides two metal-reinforced PCIe x16 slots fed by the CPU. The leftmost of these gets the full 16 lanes from an LGA 1151 CPU with a single graphics card installed. Install a second graphics or expansion card, and the board runs each of the primary PCIe x16 slots at x8 speeds.
All of the remaining PCIe slots draw their connectivity from the Z270 chipset. The board has four PCIe x1 slots running off the Z270 chip, as well as a physical PCIe x16 slot that offers x4 bandwidth. Some of these PCIe x1 slots share their lanes with the ASMedia ASM2142 USB 3.1 controller that lights up the Z270E's front-panel USB 3.1 Gen 2 header. Plug in a case's front-panel Gen 2 cable, and the second and fourth PCIe x1 slots in the image above will be disabled.
For traditional 2.5" and 3.5" storage devices, Asus offers six SATA ports running at 6 Gbps from the Z270 chipset. Some of these share bandwidth with the Z270E's twin M.2 slots, so not every port will always be available if you're using next-gen storage. More on that in a second.
The board's duo of M.2 slots are also powered by the Z270 chipset. The primary M.2 slot is smartly located under the chipset heatsink, far from any other heat-producing components that could threaten an SSD with thermal throttling. This slot supports both SATA and NVMe SSDs, but using it in SATA mode will disable the board's SATA 1 port. NVMe drives are always assured of four lanes of PCIe 3.0 from this slot at all times.
The secondary NVMe slot sits between the CPU socket and the first PCIe x16 slot. This slot is closer to the largest heat source in most modern PCs than the primary M.2 slot, but that position still beats being underneath the first PCIe x16 slot, where a drive might be torched by open-cooler graphics cards. This M.2 slot shares bandwidth with some of the Z270E's SATA connectors. Plug in an NVMe device here, and the SATA 5 and SATA 6 connectors will go dark.
Overall, the Z270E's expansion capabilities aren't spread too thin by the lane-sharing mojo of Z270. The worst-case scenario for the board involves a build with a SATA M.2 SSD in the primary M.2 slot and an NVMe SSD in the secondary M.2 slot, along with a case that has a USB 3.1 Gen 2 front-panel cable hooked up. In this situation, the Z270E loses three of its six SATA ports and two of its four PCIe x1 slots. Builders would still have ample storage and expansion options to work with even with that unlikely setup. In a more typical build with a single NVMe drive and no front-panel USB 3.1 Gen 2, the Z270E keeps six SATA ports and all of its PCIe slots working. That's good news for storage-hungry mainstream builds.