When testing the Plextor M6e M.2 PCIe SSD we noticed that it did get pretty warm. How warm? When running some benchmarks we found that the NAND chip on the far left side of the drive was around 40C and the label that was over the power management components was nearly 85C. The temperatures across the M.2 drive are vastly different and it was running a bit warmer than we expected it to be.
Until M.2 drives are able to run cooler, however, we recommend using M.2 slots that are integrated onto a motherboard only if you are able to check the drive temperature to make sure it isn't overheating. Otherwise, we recommend using a M.2 to PCI-E adapter that includes a heatsink like the one we used in our testing.
Designed for hard disk drives, the AHCI protocol doesn't support parallel processing of data access requests whereas the new NVMe is optimized for PCI Express and nonvolatile memory.
The M6e specs suggest that simply transitioning an SSD to the PCIe 2.0 x2 bus won’t ensure huge performance benefits without new controllers. The Marvell 88SS9183 chip is not the best choice for PCIe SSDs, actually. There are faster platforms even from the same Marvell, such as the 88SS9293, but Plextor doesn't seem to be willing to set new performance records.
is going to be faster because there are no intermediary (chipset or switch) between the SSD and the CPU. But the graphics card is going to work in PCIe 3.0 x8 mode in this case on LGA1150/1155 platforms, which may be unacceptable for enthusiasts.
I've also come to realise that for general everyday use, at this point in storage development, it doesn't really matter what type (SATA, M.2, SATA Express etc) or brand of SSD one uses, unless it's a Raid 0 array one isn't going to see that much of a real world difference. A tenth of a second here, maybe half a second there. Not really measurable unless one uses a stopwatch. And if you do want really fast performance, a couple of cheap SSD's is all you need.