Thermal design power

[7] Most modern processors will cause a therm-trip only upon a catastrophic cooling failure, such as a no longer operational fan or an incorrectly mounted heat sink.

Actual power usage can be higher or (much) lower than TDP, but the figure is intended to give guidance to engineers designing cooling solutions for their products.

That way, a processor can operate at higher or lower performance levels, depending on the available cooling capacities and desired power consumption.

[13] IBM's POWER8 processor implements a similar power capping functionality through its embedded on-chip controller (OCC).

[21][22][23][24][25][26] In fact, different manufacturers define the TDP using different calculation methods and different operating conditions, keeping these details almost undisclosed (with very few exceptions).

This makes highly problematic (if not impossible) to reasonably compare similar devices made by different manufacturers based on their TDP, and to optimize the design of a cooling system in terms of both heat management and cost.

On the contrary, when dealing with the Thermal Design Power (TDP), ambiguities arise because the CPU manufacturers usually do not disclose the exact conditions under which this parameter has been defined.

For instance, an Intel’s general support page states briefly that the TDP refers to "the power consumption under the maximum theoretical load".

In conclusion: In October 2019, the GamersNexus Hardware Guides[25][34] showed a table with case and ambient temperature values that they got directly from AMD, describing the TPDs of some Ryzen 5, 7 and 9 CPUs.