Some data after 12 hours of no fan. Temp: avg 62 C (~ 37 C with fan), Offset avg 2.9 ms (0.09 ms with fan), drift avg 8.46 ppm (4.4 ppm with fan) From that very limited data sample, it looks like NTP offset and drift get worse with CPU temp. Again, very little data and lots of possible unknown causation. Also, the cyclical pattern in the drift graph was still there with the absolute values of the max and min for each cycle being greater than that of the system with a fan.Good test. Won't be able to do that immediately, but will do so in the next day or so for 12 - 24 hours and see what the results are. I'll report back when I get some data.