Boot issues with HP 546SFP+ on Supermicro X11SSL-F/X11SSM-F

[onlinefloh]

Hi guys,

Not directly related to gentoo, but I figured I might as well ask the guru's here for advice.
I just managed to trigger a weird issue on a couple of my servers: In order to upgrade network bandwith, I plugged in a bunch of HP branded Mellanox ConnectX-3 10GbE Dual Port SFP+ cards (one per server).
Cards have been procured recently as NOS or refurbished from different vendors, the servers are running for a couple of years already. In a few cases (actually most of the upgraded servers...), the servers refused to boot after the upgrade, with beep code indicating RAM failure. After swapping arund network cards and RAM sticks, it apperas that IF I hit a certain combination of Mainboard (Supermicro X11SSL-F or X11SSM-F), installed RAM (more than 2 Sticks of 16GB each) and the mentioned Network Card, it reliably triggers the problem of not booting with apparent RAM issues. Reducing RAM capacity to 32 GB or removing the network card reproducibly makes the problem disappear again. RAM is a wild mix of various manufacturers (Samsung, Micron, Kingston, but always installed in matched pairs). Supermicro X10SSH or X10SSL boards are unaffected. (No, I didn't swap Memory between X10 and X11 boards as they're DDR3 vs. DDR4). Not maxing out the RAM capacity would only be viable for one or maybe two of the boxes. Any ideas?

tnx,