Get ConnectX3 or X520 SR1 for PCIe gen2 x1 slot?

you may have seen my first post:

i don’t have much choice till i can upgrade the mobo. i can get either a connext 3 for $30 or an X520 for $66.

i remember reading some where that intel NIC don’t mind the lower pcie lane/speed/slot but, the connectx’s definitely do? i can’t for the life of me remember what thread in what forum where i read this.

i have a connectx 2 that has been working but, i upgraded from server 2008 r2 to server 2019 and the connectx 2 has no drivers from mellanox which you NEED built in win drivers are too slow. unless i try win server 2012 drivers. i’ve made xp GPU drivers work in 10 before.

while i’m fiddling around to make the ConnectX 2 work with whatever older os drivers i can get from Mellanox i though about just upgrading? Mellanox hasa crazy driver and firmware scheme Intel has always been simple and reliable and usually NOT eol.