nvidia-smi reports PCIe link generation to be 3 when using 4.0 riser cables but 4 when connected directly

Question

Even more strangely, upon boot, with the cables, initially it seems to see both cards as PCIe4 - but then it immediately reverts to 3. Is there something thats causing this?

I have tried many different brand cables, behavior is the same.

• GPU 2x RTX3090

• motherboard Gigabyte mb72-hb1

• Version: 22.10 (GNU/Linux 5.19.0-35-generic x86_64)

See below for the behavior-- first is from immediately after boot (As soon as SSH works), the second is immediately after

nvidia-smi -a | grep Max
                Max                       : 4
                Max                       : 16x
        GPU Max Operating Temp            : 93 C
        Memory Max Operating Temp         : N/A
        Max Power Limit                   : 350.00 W
    Max Clocks
    Max Customer Boost Clocks
                Max                       : 4
                Max                       : 16x
        GPU Max Operating Temp            : 93 C
        Memory Max Operating Temp         : N/A
        Max Power Limit                   : 350.00 W

A few seconds later

nvidia-smi -a | grep Max
                Max                       : 3
                Max                       : 16x
        GPU Max Operating Temp            : 93 C
        Memory Max Operating Temp         : N/A
        Max Power Limit                   : 350.00 W
    Max Clocks
    Max Customer Boost Clocks
                Max                       : 3
                Max                       : 16x
        GPU Max Operating Temp            : 93 C
        Memory Max Operating Temp         : N/A
        Max Power Limit                   : 350.00 W