The OCZ RevoDrive Hybrid, a PCIe SSD with a HDD piggybacking a ride - PC Perspective
Amazon.com: PCIe SATA Card 4 Port ,PCI Express to SATA 3.0 Ports Expansion Controller Boot as System Disk for Desktop PC Support SSD and HDD with Low Profile Bracket and 4 SATA
MB839SP-B by ICY Dock - 2.5” SATA SSD/HDD to PCIe 2.0 x1 Hot-Swap Mobile Rack for PCIe Expansion Slots. PC PitStop Data Storage Solutions - SAS Enclosures, DAS, NAS, iSCSI & FC
HDD-PCI-A | Ainex
Amazon.co.jp: Sedna - PCI Express (PCIe) デュアル2.5インチ SATA III (6G) SSDアダプター (ショートダブルサイドSSDバージョン) (電源回路内蔵 SATA電源コネクタ不要 Macに最適 SSD/HDDは含まれません : パソコン・周辺機器
Seagate just unveiled the first ever PCIe NVMe hard disk drive | TechRadar