Consequently, a x16 slot (the standard for GPUs) provides approximately of bidirectional bandwidth, a substantial increase over PCIe 3.0’s 15.75 GB/s.
PCIe uses a byte-wise encoding scheme (128b/130b encoding). The theoretical bandwidth per lane is calculated as follows: $$ \text{Bandwidth} = \text{Data Rate} \times \frac{\text{Payload Bits}}{\text{Total Bits}} $$ pcie specification 4.0 pdf download
Download. 10/05/2017. 4.0. This specification describes the PCI Express® architecture, interconnect attributes, fabric management, Specifications - PCI-SIG Consequently, a x16 slot (the standard for GPUs)