6G → 9Gbps!If it is late with 10GBE NIC, fix the PCIe link width with UEFI

Is 10GBE slow if you change your PC?

　The PC was renewed earlier this year, but since then, the wired speed has been slow.

　The NIC attached to the PC is ASUS's "XG-C100C".The second PCIe 3 of the motherboard.It is attached to the 0 x16 slot (X4 mode), but even if you try iPerf3, you will be heading at a speed of about 5 to 6 Gbps.

　There was no problem in practical use, and there was no chance to measure the 10Gbps bench in the review, so I have been postponing to explore the cause, but I finally got time, so I tried to find out the cause.

　In conclusion, it was working in PCIe X1 mode.

　As mentioned above, the PCIE slot itself was in the size of the X16, and the transfer mode also supported the maximum X4, so I never thought that this was a bottleneck.However, when I checked it properly, it was unfortunately working in X1 mode.

　It's an embarrassing story, but even if you look at the overseas bulletin versions, you often see writing that the iPerf3 speed of 10Gbps NIC is around 6Gbps.If the speed is slow despite being mounted on a slot of X4 mode or higher, it is recommended that you change the UEFI settings in the procedure in this article.