Occasional realtime delay

Hi, I have my new setup running with a mesa 7i96s board and things generally seem to be working well.  However I occasionally get an "unexpected realtime delay" error upon opening Linuxcnc (maybe one out of five times opening the program) and once got a "watchdog has bit" error while the program was running (out of a total of a few hours of running). 
I've run the latency-histogram --nobase for ~6 hours and the std dev is 1.5 us and a maximum deviation of 30 us.  So most of the time, the PC seems to be doing fine.  Also, I installed an additional network card so that I could simultaneously be connected to the mesa board and my network.  I don't remember getting any of these errors before adding this card.  Maybe that has something to do with it? Any guesses on this very occasional, unexpected latency?  I'm tempted to ignore it. I've disabled all the power management features I could see in the BIOS.  I haven't fiddled around with preempt-rt configurations. 

Thanks for your help,
Carson

What host PC do you have?

Have you disabled all power saving/Cstates >C1, Turbo modes and hyperthreading in the BIOs?

If there is a Intel  Ethernet chip connected to the 7I96S,  is IRQ coalescing disabled? (man hm2_eth)

If you still have issues, using isolcpus to isolate a core for LinuxCNC and pinning the Ethernet
IRQ to that core helps a lot with network latency:

forum.linuxcnc.org/38-general-linuxcnc-q...irq-affinity?start=0