I wouldn't necessarily count on the system temp being a false reading - I was able to get a motherboard up to 109 C on the northbridge/VRMs before it automatically shut down, and those were definitely genuine temps. The OP says his motherboard only has two slots for RAM, which tends to suggest it's an extreme budget model, possibly without a hard shutdown feature for sky high system temps.
If I were you then more screenshots of the Speedfan temps at idle could be useful. Also, opening the case and having a desktop fan blowing inside would probably enormously reduce the VRM/Northbridge system temp (if it is reading properly). It'd be interesting to see if it still stutters the same with that ruled out.
If I were you then more screenshots of the Speedfan temps at idle could be useful. Also, opening the case and having a desktop fan blowing inside would probably enormously reduce the VRM/Northbridge system temp (if it is reading properly). It'd be interesting to see if it still stutters the same with that ruled out.