hmm, interesting, prob not 4g encoding if you boot all cards into windows successfully anyways actually now that i think about it

system interrupts are caused by hardware/driver errors, and they can eat up resources till your PC crashes
if you have a faulty riser, you can get them, but they wont start till you start mining .
you will see in task manager "system interrupts" with high cpu usage
solution for them is update drivers (system drivers not GPU)/replace faulty riser usually