Specifications:

Conforms to Serial ATA 3.0 specification, backward compatible with SATA2.0 SATA1.0 Follow PCI- Express v2 .0 specification and backward compatible with PCI-Express v1.0.
Supports communication speeds of 6.0 Gbit / s, 3.0 Gbit / se 1.5 Gbit / s Supports Gen 1i, Gen 1x, Gen 2i, Gen 2m, Gen 2x and Gen 3i.

Supports AHCI1.0 mode and IDE mode Supports native command queue (NCQ)

Supports FIS based on port multiplier switch or command switch.

Supports hot swap.
Compatible with SATA6G, 3G and 1.5G hard drives PCIE 3.0 SATA Controller Solution About the Speed Description The best effect can be achieved with SATA3.0 data cable.

PCI-E requires a slot higher than V2.0.

For V1.0, the speed will not exceed 250 M.

Regardless of whether PCI-E is 4x or 16x, you can put it directly into the free 16x slot, provided it is the V2.0 version. It does not support PCI-E 1x.
The motherboard setting BOIS:

SATA mode must be changed to AHCI.

Although some motherboards are PCIE version 2.0, by default BOIS does not enable gen2 high-speed mode, which must be enabled manually.

The maximum speed of PCI-E 2.0 is 380-450 m/s. When connected to PCI-E1.0, the speed is only 200-300 m / s.
Different computer configurations and SATA SSDs have different speeds.