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The term “PCIe lanes” can be applied to two different attributes of a PCIe device.

Lanes are designated by the “x” symbol after “PCIe”. For example, PCIe x16 – this refers to 16 lanes.

However, PCIe lane value of “x” can refer to either the electrical or physical attribute of the device. These ratings are not always 1:1. For example, a PCIe x8 device can be installed into any slot with x8 or x16 physical lanes, even if those slots are only able to provide x1 electrical lanes.

Electrical lanes – this determines the performance capabilities of the device. This value represents the number of electrical PCIe lanes the device requires in order to perform optimally. However, a lower electrical rating will not generally prevent the device from functioning.

Physical lanes – this refers to the physical size of the PCIe slot required by the device. For example, a physical PCIe x4 device can be installed into a physical PCIe x4, x8 or x16 slot, but could not be installed into a physical x1 slot.

As a general rule, a PCIe device’s electrical lane rating is the easiest way for most users to determine the minimum physical lane requirement. However, it if performance is your chief concern, always make sure to install the device into a motherboard PCIe slot that has an electrical lane rating greater than or equal to the PCIe device.

• A PCIe device with x16 electrical lanes can only be installed into physical x16 slot.
• A PCIe device with x1 electrical lanes can be installed into any PCIe slot.
• A PCIe device with x8 electrical lanes can be installed into either an x8 or x16 physical slot. However, in order for the device to perform optimally, the x8 or x16 physical slot must be capable of providing x8 or more electrical lanes.