前言
如果打算撿張便宜的 10G 網卡，但主機板只有 PCI-E x1 插槽，那麼可以嘗試使用轉接卡來解決這個問題。
由於 PCI Express 介面的向下相容性，所以可以在 PCI-E x1 插槽上使用 PCI-E x8 的 10G 網卡。
須要留意現時大多數 ITX 主機版上的 PCI-E x1 插槽都是 2.0 版本，理論上 PCI-E 2.0 x1 最高只可以支援到 500 MB/s 的傳輸速率。
雖然轉接卡後有最大傳輸速率的限制，但是 10Gbps 網卡的性能還是要比 2.5Gbps 網卡好一些。
如果打算用轉接卡，撿 10G 網卡時最好選半高的，因為機殼的空間有限，全高的網卡可能裝不下。
PCI Express 匯流排效能
| Version | Year | Line Code | Transfer Rate | Bandwidth (×1) | Bandwidth (×2) | Bandwidth (×4) | Bandwidth (×8) | Bandwidth (×16) |
|---|
| 1.0 | 2003 | 8b/10b | 2.5 GT/s | 250 MB/s | 0.50 GB/s | 1.0 GB/s | 2.0 GB/s | 4.0 GB/s |
| 2.0 | 2007 | 8b/10b | 5.0 GT/s | 500 MB/s | 1.0 GB/s | 2.0 GB/s | 4.0 GB/s | 8.0 GB/s |
| 3.0 | 2010 | 128b/130b | 8.0 GT/s | 984.6 MB/s | 1.97 GB/s | 3.94 GB/s | 7.88 GB/s | 15.8 GB/s |
| 4.0 | 2017 | 128b/130b | 16.0 GT/s | 1969 MB/s | 3.94 GB/s | 7.88 GB/s | 15.75 GB/s | 31.5 GB/s |
| 5.0 | 2019 | NRZ 128b/130b | 32.0 GT/s | 3938 MB/s | 7.88 GB/s | 15.75 GB/s | 31.51 GB/s | 63.0 GB/s |
| 6.0 | 2021 | PAM4 & FEC FLIT 1b/1b | 64.0 GT/s | 7877 MB/s | 15.75 GB/s | 31.51 GB/s | 63.02 GB/s | 126.03 GB/s |
Wikipedia: PCI Express 匯流排效能
iperf3 測試結果
10Gb 2.0 x8 <-> 2.5Gb PCI-E
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| Connecting to host 192.168.10.100, port 5201
[ 5] local 192.168.10.127 port 58316 connected to 192.168.10.100 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 290 MBytes 2.43 Gbits/sec 0 348 KBytes
[ 5] 1.00-2.00 sec 282 MBytes 2.37 Gbits/sec 0 468 KBytes
[ 5] 2.00-3.00 sec 282 MBytes 2.37 Gbits/sec 0 348 KBytes
[ 5] 3.00-4.00 sec 282 MBytes 2.37 Gbits/sec 0 339 KBytes
[ 5] 4.00-5.00 sec 284 MBytes 2.38 Gbits/sec 0 339 KBytes
[ 5] 5.00-6.00 sec 282 MBytes 2.37 Gbits/sec 0 339 KBytes
[ 5] 6.00-7.00 sec 282 MBytes 2.37 Gbits/sec 0 345 KBytes
[ 5] 7.00-8.00 sec 282 MBytes 2.37 Gbits/sec 0 359 KBytes
[ 5] 8.00-9.00 sec 282 MBytes 2.37 Gbits/sec 0 334 KBytes
[ 5] 9.00-10.00 sec 280 MBytes 2.35 Gbits/sec 0 368 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 2.76 GBytes 2.38 Gbits/sec 0 sender
[ 5] 0.00-10.05 sec 2.76 GBytes 2.36 Gbits/sec receiver
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10Gb 2.0 x8 <-> 2.5Gb USB
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| Connecting to host 192.168.10.101, port 5201
[ 5] local 192.168.10.127 port 34542 connected to 192.168.10.101 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 290 MBytes 2.43 Gbits/sec 0 348 KBytes
[ 5] 1.00-2.00 sec 282 MBytes 2.37 Gbits/sec 0 342 KBytes
[ 5] 2.00-3.00 sec 280 MBytes 2.35 Gbits/sec 0 339 KBytes
[ 5] 3.00-4.00 sec 282 MBytes 2.37 Gbits/sec 0 342 KBytes
[ 5] 4.00-5.00 sec 282 MBytes 2.37 Gbits/sec 0 339 KBytes
[ 5] 5.00-6.00 sec 282 MBytes 2.37 Gbits/sec 0 342 KBytes
[ 5] 6.00-7.00 sec 282 MBytes 2.37 Gbits/sec 0 342 KBytes
[ 5] 7.00-8.00 sec 282 MBytes 2.37 Gbits/sec 0 336 KBytes
[ 5] 8.00-9.00 sec 282 MBytes 2.37 Gbits/sec 0 351 KBytes
[ 5] 9.00-10.00 sec 274 MBytes 2.30 Gbits/sec 0 5.70 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 2.76 GBytes 2.37 Gbits/sec 0 sender
[ 5] 0.00-10.04 sec 2.75 GBytes 2.35 Gbits/sec receiver
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10Gb 2.0 x8 <-> 10Gb 2.0 x1
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| Connecting to host 192.168.10.200, port 5201
[ 5] local 192.168.10.127 port 56738 connected to 192.168.10.200 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 408 MBytes 3.42 Gbits/sec 13 354 KBytes
[ 5] 1.00-2.00 sec 402 MBytes 3.38 Gbits/sec 11 339 KBytes
[ 5] 2.00-3.00 sec 402 MBytes 3.38 Gbits/sec 0 348 KBytes
[ 5] 3.00-4.00 sec 402 MBytes 3.38 Gbits/sec 0 348 KBytes
[ 5] 4.00-5.00 sec 402 MBytes 3.38 Gbits/sec 0 339 KBytes
[ 5] 5.00-6.00 sec 401 MBytes 3.37 Gbits/sec 0 339 KBytes
[ 5] 6.00-7.00 sec 402 MBytes 3.38 Gbits/sec 0 354 KBytes
[ 5] 7.00-8.00 sec 404 MBytes 3.39 Gbits/sec 0 322 KBytes
[ 5] 8.00-9.00 sec 402 MBytes 3.38 Gbits/sec 0 328 KBytes
[ 5] 9.00-10.00 sec 389 MBytes 3.26 Gbits/sec 0 5.70 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 3.92 GBytes 3.37 Gbits/sec 24 sender
[ 5] 0.00-10.04 sec 3.92 GBytes 3.35 Gbits/sec receiver
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常見問題
如果網絡中其中一方使用的網速遠低於 10Gbps，有可能會出現大量的重傳，這時候可以嘗試調整網卡的設定解決這個問題。
最佳化 10Gbps+ 網卡的系統效能和常見問題，可以參考 最佳化 10Gbps+ 網卡的系統效能。
