What is PCIe SW

Peripheral Component Interconnect express (PCIe), you may have seen this name on motherboards. Do you know PCIe Switch that uses this standard?

PCIe SW was originally a standard for accessing memory from the CPU, but now it is often used for servers and storage. In addition, even within the industry, which has not shown interest in high-speed communication, attention is now focused on high-speed communication as the amount of data increases with the advent of high-precision cameras and 5G. In this article, we will explain in order while focusing on the basic functions and features of PCIe SW.

PCIe architecture

In the explanation so far, I have explained the relationship between RC and EP in PCIe and the Config space that sets them so that you can imagine the whole picture. From the third installment, we will explain the architecture of PCIe, which is the standard used for PCIeSW.

The PCIe architecture has a layered structure, and each layer has a clearly defined role. The software layer defines drivers and applications, the transaction layer defines data transmission and reception, and the data link layer defines communication management with the communication partner. Because it is divided into roles in this way, it is said that it is easier to change and expand product specifications than PCI.

In PCIe communication, data is handled in a data format called a packet. Since this packet exchanges layer by layer, information is added as it passes through the lower layers during transmission, and information is deleted as it passes through the upper layers during reception. This makes it possible to exchange data for each corresponding layer.

Packets for each layer are also called Transaction Layer Packet (TLP), Data Link Layer Packet (DLLP), and Physical Layer Packet (PLP), respectively.

In Part 3, I briefly explained the architecture of PCIe. In the 4th article, I will continue to explain the basic knowledge related to PCIeSW.

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