Thermal Dynamics
To find the UX331UN's idle temperature, we left Windows on the desktop for 30 minutes. The ‘load’ temperature reading comes from running 3DMark Fire Strike.
The UX331UN runs a little hot when idle, although 46C for the CPU is nothing to be too worried about. The 82C temperature at full pelt is also quite toasty, but just about on the right side of acceptable. We didn't see any signs of throttling when we were gaming on this laptop.
Acoustics
The UX331UN is essentially inaudible when idle or performing only moderate tasks. When the fan spins up, it's evident in a silent room but if there is any other background noise it won't be noticeable. This is the plus side of the lower clock speeds than possible for the NVIDIA GeForce MX150 graphics.