For some time now, my PC has been freezing periodically - about once every 2 days, the screen looks normal, but mouse, keyboard etc. do not respond and I have to hold the power key in to restart.
By process of elimination, the culprit appears to be the Xeon Phi 3120A card - I just took the card out and ran the PC for a month without a freezing incident.
Put it back in and it froze the same day.
I have tried it in both possible expansion slots - froze with both.