Bottleneck - PCIe gen 3 x1 device on PCIe gen2 x2 slot
Is there a bottleneck between a device with PCIe gen 3 x1 connection if connected to a PCIe gen2 x2 slot?
1 Answer
PCIe x1 means that you have (or your card has) only one lane available. As one side of your connection is "x1" then you are limited to 1 lane.
The PCIe generation defines the maximum supported speed per lane, per the PCIe spec. A PCIe Gen 2 motherboard cannot work at Gen 3 speeds because it lacks the necessary (newer) hardware to do so.
As a result your card will be limited to PCIe Gen 2 x1 as it only has one lane available.
This means you are limited to 500 MB/s (PCIe V2 x1) instead of 985 MB/s (PCIe V3 x1).
Whether that is an actual bottleneck depends on what the card is and how much data you expect to put through it every second. For a video capture card (~50Mbit/s for FullHD h.264) or sound card (1-2MB/s), even a gigabit network card (1Gbps or 125MB/s), this speed is fine.
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