When it comes to AMD the normal temp is quite a bit complicated some X2s work at about 42c fully loaded some works around 50c (the same nm and model),but i know for X2s everything under 52c is OK(with stock HSF) is you could stand loud fan noise.
You may check newegg reviews also.
S939 X2s run at something like 48-55°C depending on the Vcore; the first ones used 1.40V while later they dropped to 1.35V. Socket AM2 versions have a wider temp range because they have normal and low power models. Normal models are slightly cooler than the S939 versions because their specs are 1.30-1.35V while low power ones run @ 1.20-1.25V, resulting in the ~42° you mention. The cool thing with most of the latest AM2 X2s is that they are low power chips even if they're not rated as such, so they're either good 2.8-3.0G overclockers with almost stock 1.40-1.45V, or you can bring their Vcore down to 1.20V @ stock speed and drop the temps as much as 10°C to make them fit nicely in a HTPC.