One end of the PCIe connection is the host device, usually the CPU or chipset on the motherboard; the other end is peripheral devices, such as graphics cards, SSDs or network cards, etc.

PCIe (Peripheral Component Interconnect Express) is a high-speed serial computer expansion bus standard used to connect the motherboard and various peripheral devices. Only one device can be connected to each end of a PCIe link, and these two devices serve as the data transmitter and receiver for each other. The following is a detailed explanation of PCIe:

1. Hierarchical Structure: The hierarchical structure used by the PCIe bus is similar to that of the network protocol stack and consists of multiple layers. When the transmitting end sends data, it will go through these layers, and the receiving end also uses these layers when receiving data. This design makes data transmission efficient and reliable.
2. End-to-End Data Transmission Method: In a data path (Lane) of the physical link, it is composed of two sets of differential signals, that is, a total of 4 signal lines. Each device contains transmitting logic (TX) and receiving logic (RX), ensuring that data can be safely transmitted from one device to another.
3. Point-to-Point Connection: Different from the early PCI bus, PCIe adopts a point-to-point connection method, which means that each device communicates directly with the motherboard without going through other devices. This can reduce the latency in the data transmission process and improve the bandwidth utilization.

In general, the PCIe interface, with its high-speed and efficient data transmission characteristics, has become an indispensable part of modern computers. It allows various types of peripheral devices to exchange data with the computer at a very high speed, thereby enhancing the performance of the entire system.