U. 3 is a Tri-mode standard, building on the U. 2 spec and using the same SFF-8639 connector. It combines SAS, SATA and NVMe support into a single controller. Where firmware support is available, U. 3 can also support hot-swap between the different drives.. The pci-e 1x card work for U. 2 and U. 3 SSD, not work for SATA/SAS SSD.. The speed and other properties is not changed, only form conversion interface. Transparent to the operating system and does not require any software drivers.
. U. 3 drives are still backward compatible with U. 2, thoughthe U. 3 drives determine which host type it is inserted into (by using different combinations of HPT0 and HTP1 being open or ground), and configure the data lanes on power-up. U. 3 drives can still act as dual-port NVMe drives in supporting systems.. This PCI Express card expands the PC by one U. 2/U. 3 SFF-8639 interface. It can be connected e. g. the U. 2/U. 3 U3 PM1735 Series SSD.