variability in WU size recently.

my gtx 1080 on windows is taking any where from 170 to 600 seconds to complete a single WU.
here is the host in question: https://sech.me/boinc/Amicable/resul...state=4&appid=


Up until a few days ago it took ~170 seconds on every WU.
I have checked other host and some show this type of activity and some do not.

What am i missing here? Why is this happening?

is it a windows thing, my Linux hosts are still taking ~170 seconds per WU every time.