TechPowerUp writes that even though Intel's X99 chipset supports as many as ten SATA 6Gbps ports on paper, it seems only six have full functionality. The latest driver makes only six of the ten SATA 6Gbps ports visible to the operating system, the other four ports become visible as part of a separate controller, only when a device is plugged into them. These four ports can't use the same SATA power management features as the first six ports, nor can they be part of a RAID array with drives plugged into the first six ports.
This isn't the first time Intel has issues with storage on its high-end chipset, the X79 had a similar issue that caused motherboard makers to release products with fewer SATA/SAS ports than the platform was capable of.
Intel withdrew version 220.127.116.116 of its RSTe drivers (even from the list of older drivers), and made its motherboard partners do the same. Replying to German publication Heise.de, ASUS explained that the driver was withdrawn because it doesn't support ATA TRIM command for SSDs striped in a RAID 0 array. The latest driver makes only six out of ten SATA 6 Gb/s ports visible to the operating system, and you can create RAID arrays using on these six ports. The other four ports become visible as part of a separate controller, only when a device is plugged into them. This controller is recognized by Windows' internal Standard AHCI controller driver. This also means that the four ports don't benefit from the SATA power management features the first six ports do, nor can they be part of a RAID array with drives plugged to the first six ports. Intel did not respond to the Heise article.