Also of note while researching the issues I was having with the x520 cards i found this gem! https://forums.servethehome.com/index.php?threads/patching-intel-x520-eeprom-to-unlock-all-sfp-transceivers.24634/ Change your eeprom to allow SFP's from any manufacturer not just Intel. Works really well o...

Same thing i have a Intel X520 DA1
Tested multiple DAC and Transceiver.
2.12 didn't work
2.13rc12 worked

also tested an other 2.13 from support and didn't work.

Switch always show( even with the broken firmwares) link up and show info from DAC and Transceiver