I have a slightly overclocked i5 running at 3.2ghz. At idle, Cores 0/1/3 all run at around 35c but Core 2 flirts in the low 40 range. Running prime 95, no core goes above 51c, all seem to stay at around that level.
Is the temperature differentiation due to uneven thermal paste? Is it a big enough idle temperature difference to warrant a reapplication of thermal paste?
It's perfectly normal, the sensors are not precision calibrated. 1 degree in actual temperature change doesn't necessarily mean 1 degree change in the reading because the sensors don't scale linearly with temperature. The lower the actual temperature, the poorer the accuracy.