What is PCIe and how does it work?

PCIe (Peripheral Component Interconnect Express) is an interface standard for connecting high-speed components created by the industry consortium PCI-SIG

In its simplest form, PCIe is a point-to-point connection between two PCIe-compatible devices, typically a motherboard and a graphics card or SSD. The connection provides speeds of up to 32 GT/s using differential signaling to transmit data over separate pairs of copper wires.

PCIe is an important standard in today's computer systems. It is used for a variety of applications, such as connecting storage devices, graphics cards, and other peripherals. PCIe enables higher data transfer speeds than other standards such as PCI, USB, or SATA.

It also provides a more reliable and efficient form of communication between components, reducing latency or stuttering. It also allows multiple peripherals to be connected simultaneously with minimal latency.

Each combination of processor and chipset has a limited number of these PCIe lanes.

For example, 13th generation Intel processors have 18 PCIe lanes (16*PCIe 5.0 and 12*PCIe 4.0), and the Z790 chipset has 28 PCIe lanes.

These lines are divided between the CPU/chipset links (8 in our example above) and the various connectors, such as PCIe slots for expansion cards or M.2 slots for SSDs. They can also be used to add additional USB, SATA, network or audio controllers if the ones built into the chipset are insufficient.

Every desktop PC motherboard has a number of PCIe and M.2 slots. You can use the former to add GPUs (video or graphics cards), RAID cards, and Wi-Fi cards, and the latter forNMVe (solid-state drive) SSDs. The type and number of PCIe slots available on your PC depends on the motherboard you choose.

PCIe comes in different configurations, such as x1, x4, x8, and x16. These numbers after the x indicate the number of lanes the PCIe slot has. A PCIe x1 slot has one lane and can move data at a rate of one bit per cycle. A PCIe x2 slot has two lanes and can move data at a rate of two bits per cycle (and so on).

You can insert a PCIe x1 card into a PCIe x16 slot, but that card will only receive the bandwidth of one lane. Similarly, you can put a PCIe x8 card in a PCIe x4 slot, but it will operate at half the maximum bandwidth of a PCIe x8 slot. Most GPUs require a PCIe x16 slot to operate at full speed, and M.2 SSDs require a PCIe x4 slot.

Here's a summary of the generation specifications:

The good news is that all generations of the PCIe standard are backward compatible.

This means that there will be no compatibility issues between a port and a card of a different generation, higher or lower. However, in the case of a lower-generation port, the maximum data rate is limited by that port's generation. You'd be losing performance.