The Fujitsu Futro S920 is based on the same motherboard as the S720. I don't have a S920 but the S720 entry will provide you with some of the technical details on the motherboard that it uses (D3313).
At the end of 2023 I received an email from Gábor about the PCIe speed on the S920. Before handing over to him I would note that over time the PCIe standard has evolved with each new release doubling the potential transfer speeds. The AMD CPUs used on the motherboard support the Generation 2.0 of the standard which has a maximum transfer speed of 5 GT/s.
Gábor emailed:
I have a couple of units with D3313-A13 GS 1 motherboards. I think the issue I found will also be the same for the the S720 and S520. By default the PCIe is running with 2.5 GT/s transfer speed. That isn't a big problem with WLAN cards, but when you have an S920 and you want to implement a fast router, this speed isn't enough.
There is no option in the BIOS to set the speed to 5GT/s, but there is a Fujitsu tool exists to change many settings. This includes the PCIe speed. This tool is named EditCMOS. There is no need to install an updated BIOS, this tool is making changes directly in the flash chip. You can download a copy from here: https://intstudio.hu/etc/EditCmos.zip
I note that the EditCmos utility is downloadable from the Fujitsu support site (ftp.kontron.com) but the
zip file is password protected and the accompanying readme.txt file does include the line:
Restricted Access, please contact your mainboard distributor for password details.
i.e. The unprotected zip file is not intended to be generally available.
In August 2024 I had an email from fanoush expanding a little further on the topic:
I already had a copy of EditCmos.exe so didn't bother to download the zip file - a mistake. The EditCmos zip file linked to above includes supporting text along with a pcie.bat file for setting the S920 PCIe speed.
What I discovered initially is posted at www.servethehome.com with a further comment here. Basically what you do is to boot DOS/FreeDOS and execute the command:
EditCMOS.exe SetID:0x01B7=0x0151.