I recently bought a Minisforum MS-A2 and I wanted to add some extra 2.5gbps ethernet ports to it. I looked around and found the GLOTRENDS ST7419 which is described as "ST7419 4-Port RJ45 2.5Gb Ethernet Network Card with Intel 1226 Controller, PCIE 3.0 X4 Interface". Note the PCIE 3.0 interface.
https://www.glotrends-store.com/products/st7419-4-port-rj45-25gb-ethernet-network-card-with-intel-1226-controller,-pcie-30-x4-interface
Once I started using it, I experienced absurd ping times of tens or hundreds of millseconds, that should have been ~1ms.
vyos@vyos:~$ ping 172.16.5.1
PING 172.16.5.1 (172.16.5.1) 56(84) bytes of data.
64 bytes from 172.16.5.1: icmp_seq=1 ttl=64 time=671 ms
64 bytes from 172.16.5.1: icmp_seq=2 ttl=64 time=37.2 ms
64 bytes from 172.16.5.1: icmp_seq=3 ttl=64 time=529 ms
64 bytes from 172.16.5.1: icmp_seq=4 ttl=64 time=557 ms
64 bytes from 172.16.5.1: icmp_seq=5 ttl=64 time=53.3 ms
64 bytes from 172.16.5.1: icmp_seq=6 ttl=64 time=92.7 ms
64 bytes from 172.16.5.1: icmp_seq=7 ttl=64 time=355 ms
64 bytes from 172.16.5.1: icmp_seq=8 ttl=64 time=212 ms
64 bytes from 172.16.5.1: icmp_seq=9 ttl=64 time=88.4 ms
I have spent a lot of time trying to solve this problem, assuming that there was a problem with a BIOS setting or a linux kernel setting that would make this work properly. After some time I swapped it from an AMD machine to an Intel one - ping issues continued.
One thing that stands out when you run lspci under Linux is that you see that there's a PCIE2 switch which connects the 4 I226-V controller to the PCIE bus. That's right, a PCIE2 switch on a device claiming PCIE3 support.
07:00.0 PCI bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch
08:01.0 PCI bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch
08:02.0 PCI bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch
08:03.0 PCI bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch
08:04.0 PCI bridge: Pericom Semiconductor PI7C9X2G608GP PCIe2 6-Port/8-Lane Packet Switch
09:00.0 Ethernet controller: Intel Corporation Ethernet Controller I226-V (rev 04)
0a:00.0 Ethernet controller: Intel Corporation Ethernet Controller I226-V (rev 04)
0b:00.0 Ethernet controller: Intel Corporation Ethernet Controller I226-V (rev 04)
0c:00.0 Ethernet controller: Intel Corporation Ethernet Controller I226-V (rev 04)
The datasheet for the PI7C9X2G608GP confirms that it is a PCIE2 device not PCIE3. https://static.datasheets.com/doc/3835518-diodes-pi7c9x2g608gpbnjex-ds.pdf
It seems like the GLOTRENDS ST7419 is a dud.