PCIe determine how much data can move between computer component, and the PCIe connection determine how well the graphics and storage drive perform. The data moves through PCIe lanes. Each PCIe lane allow data to move in both directions.
An x16 PCIe slot contain sixteen PCIe lanes, and an x4 PCIe slot contains four PCIe lanes. PCIe lanes determine the theoretical maximum data speed for the component. Data movement also depends on an PCIe generation.
How PCIe Lanes, Slots, and Generations Affect Speed
The newer the PCIe generation, the more data that can move through the PCIe lanes. However, if a device with a high generation is placed into a PCIe slot with a lower generation, the device will move less data than if it was connected to a PCIe slot with the same generation. Storage drives benefit significant from the PCIe standard.
The storage drive will reach a maximum speed when it is connected to an older PCIe interface that is lower than the maximum speed of a newer PCIe interface. The difference in speed between drives is noticeable when moving large file or when multiple drives is installed on the computer. Many motherboards has multiple M.2 slots for storage drives.
However, the PCIe speed isnt the same for all M.2 slots on a motherboard. Installing a high-speed storage drive into an M.2 slot with lower PCIe lanes or generations will force the drive to work at a lower speed. The same principle applies to PCIe and network or capture devices, though they use less data movement or bandwidth.
Graphics cards depend on PCIe lanes and generations for data movement. High-end graphics cards require a significant amount of data movement. When installing a high-end graphics card into an older PCIe slot, the graphics card will exhibit lower frame rates.
This is especially true when using high resolutions for the monitor as the graphics card will have to move more textures on the screen. Graphics cards in the mid-range use less data movement than high-end graphics cards. Therefore, they are less affected by the PCIe generations but need an adequate number of PCIe lanes to function at peak performance.
Many people make the mistake of thinking that all PCIe slots on the motherboard are the same. However, many are not. Some PCIe slots are directly connected to the processor, and some are connected through the chipset.
The chipset connection to the PCIe slots will affect the available bandwidth for other devices using the PCIe connection. Another mistake people will make is installing a fast storage drive into a PCIe slot that will work with the drive but will force the storage drive to work at a lower speed since the processor or the BIOS of the system are not set up for the newer generations of the PCIe standard. These issues wont give any error messages on the monitor.
However, the motherboard manual will provide information on the correct PCIe slot for each device. Some computer components will use more PCIe bandwidth than others. For instance, a WiFi or sound card will use the least amount of PCIe data movement bandwidth.
Therefore, they will work in any PCIe slot. A modern network or USB data connector will require a moderate amount of PCIe bandwidth. They will work best in a mid-range PCIe slot.
Finally, PCIe bandwidth is required in the highest amount for storage drives and graphics cards. The generation and number of available PCIe lanes will significantly affect their performance. The PCIe standard is backward compatible with other PCIe standards.
This means that older PCIe devices can work in a newer PCIe slot, and newer PCIe devices can work in an older PCIe slot. However, when a device of a higher generation of PCIe is placed into an older PCIe slot, the device will work at the speed of the old PCIe slot. Each new generation of PCIe roughly doubles the data that can be transferred at the PCIe speed of the previous generation.
When the devices are connected, the PCIe connection will automatically negotiate the data speed. This will not produce any error messages on the screen. However, the device will work at a reduced speed.
People should of noticed the reduction in the performance of the device in comparison to another device using a different PCIe connection.