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    Is my math correct about PCIe bandwidht and 10Gbps NICs ?

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    • M
      mcury Rebel Alliance
      last edited by mcury

      aca7c3fa-f00e-460d-9819-f0cbac96fa54-image.png

      Math for slot PCIe 3.0 x4 |10 Gbps NIC PCI 3.0 x4

      Network card:
      10 (Gbps) = 1.25 GB/s per second in half-duplex or 2.5GB/s full-duplex.

      10Gbps NIC full duplex = 2.5GB/s
      SLOT PCIe 3.0 x4 = 8GB/s

      Conclusion: If I get a 10 Gbps NIC PCIe 3.0 x4, it will use 2.5GB/s full duplex which won't be throttled by the PCIe slot. I could even get a two slot card because it would use 5GB/s maximum of the 8GB/s of the slot.

      Math for slot PCIe 3.0 x4 | 10 Gbps NIC PCI 2.0 x8 (it will run in PCIe 2.0 x4).

      Network card:
      10 (Gbps) = 1.25 GB/s per second in half-duplex or 2.5GB/s full-duplex.

      10Gbps NIC full duplex = 2.5GB/s
      SLOT PCIe 2.0 x4 = 4GB/s

      Conclusion: If I get a 10Gbps NIC PCIe 2.0 x8 and run it on PCI 2.0 x4, it will use 2.5GB/s full duplex, which won't be throttled by the PCIe slot.
      I could get a dual port 10Gbps NIC but it would be throttled by the slot in about 1GB/s.

      dead on arrival, nowhere to be found.

      stephenw10S 1 Reply Last reply Reply Quote 1
      • stephenw10S
        stephenw10 Netgate Administrator @mcury
        last edited by

        @mcury said in Is my math correct about PCIe bandwidht and 10Gbps NICs ?:

        I could get a dual port 10Gbps NIC but it would be throttled by the slot in about 1GB/s.

        Only if you are trying to use both ports at full duplex. Which very rarely happens IMO.

        M 1 Reply Last reply Reply Quote 2
        • M
          mcury Rebel Alliance @stephenw10
          last edited by mcury

          @stephenw10 said in Is my math correct about PCIe bandwidht and 10Gbps NICs ?:

          Only if you are trying to use both ports at full duplex. Which very rarely happens IMO.

          Thanks Stephen, I will get one of those.. 👍

          I have an AMD B550 chipset, which the DMI connection (from chipset to CPU), is PCI 3.0 x4.
          I have doing some math with that also, and even using a NVME PCI 3.0 and a few SATA drives, won't saturate that link with this NIC (single port).
          I have also a NVME PCIe 4.0, but that is directly connected to the CPU, so no chipset lanes used here.

          I will use it in my server, connect it directly to a USW-Enterprise-PoE-8 switch through a DAC cable since local users will be connecting to it using 2.5Gbps ports, and also some connections from the Internet.

          dead on arrival, nowhere to be found.

          1 Reply Last reply Reply Quote 1
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