I am pretty sure it's a 6122F - I've read somewhere on this forum that 6122Fs have silver heatsinks and 5122Fs have black ones, but it ought to be the same chip underneath (SFC9020?) so the distinction is probably rather moot at this point. To emphasise once again - there are two phy NICs with two ports each in two slots; that accounts for the four adapters but I can't understand why some ports are seen as 5122F and some as 6122F. I've tried switching NIC boot mode in BIOS from `Option ROM and UEFI` to `UEFI only` but that didn't change anything.
As far as performance goes, I can't make out any difference - all four ports are capable of reaching 10 G speeds without a problem. I've tested this with `iPerf3`. Tested from a Win10 box (client) to a Proxmox box (server) and I was able to max out the link (see screenshot below for spikes on all four ports with the same cable and transceiver). `iPerf3` on Windows is working in emulation mode. Windows does not make Posix calls but iperf3 understands only Posix so there's some adapting going on, and it usually took around 10 threads to max out the link consistently. Once I get a Linux box up and running, I may retest this.