The Industrial Raspberry Pi Forum

All Raspberry Pi models perform a degree of thermal management to avoid overheating under heavy load. The SoCs have an internal temperature sensor, which software on the GPU polls to ensure that temperatures do not exceed a limit which we define as 85°C on all models. It is possible to set this to a lower value, but not to a higher one. As the device approaches the limit, various frequencies and sometimes voltages used on the chip (Arm, GPU) are reduced. This reduces the amount of heat generated, keeping the temperature under control.

When the core temperature is between 80°C and 85°C, the Arm cores will be progressively throttled back. If the temperature reaches 85°C, both the Arm cores and the GPU will be throttled back.