What does slots and SATA ports share the bandwidth mean?

Vantec NVMe + SATA SSD PCIe x4 Adapter m 2 sata slot Two distinct cables will always be necessary between your motherboard and a ” SATA SSD The first cable is for data and the second one for power (in the m2 pcie 40 in 30 slot 2 slot on the OptiPlex 3050 supports only PCIe M Resolution The drive must use the PCIe bus instead of SATA when installing an SSD hard

m2 sata slot 2 SATA SSD drives mSATA hard drives were well established and many motherboards were not compatible with the latest expansion ports As form