For our temperature testing, we measure the peak GPU core temperature under load. A reading under load comes from running Metro Exodus Enhanced Edition for 30 minutes.
Older data is represented by the greyed-out bars on the above chart.
Thermal performance is where things get really interesting. Despite the unique liquid cooling approach with the built-in radiator, the Acer 4090 proved to be the hottest-running 4090 we have tested – the GPU hit just below 76C, with the hot-spot at 85C. The results are still well within safe limits, but they're about 10C hotter than a typical air-cooled card like Palit's 4090 GameRock OC, while MSI's Suprim Liquid X shows what a 4090 using an external 240mm radiator is capable of.