SK Hynix has been in the NAND and SSD business for a long time, but we haven't had the opportunity to review a drive with SK Hynix NAND in years. In most respects, SK Hynix fared the worst with the transition to 3D NAND, and their 3D NAND has not been used in very many SSDs aside from their own models. SK Hynix 3D NAND has been considerably more popular in mobile applications like smartphones and memory cards, and their client OEM SSDs are widespread but not sampled for review. This year, SK Hynix decided to start competing directly in the retail SSD market by introducing the SK Hynix Gold S31 SATA SSDs. (Outside North America, SK Hynix has been selling some SSDs under subsidiary brands.)
The Gold S31 showcases SK Hynix's vertical integration with the NAND, DRAM, controller and firmware all produced in-house. Samsung is the only other company that regularly produces SSDs with this degree of vertical integration; Micron uses third-party controllers for most of their SSDs, and the other NAND manufacturers have in-house controllers but don't make their own DRAM.
