Editing Thermal design power (section)

=== Issues when dealing with the thermal design power (TDP) ===
Once all the input data is known, the previous formula allows to choose a [[CPU]]’s [[heat sink]] with a suitable thermal resistance Rca between case and ambient air, sufficient to keep the maximum case temperature at or below a predefined value Tc.  

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. The maximum acceptable case temperature Tc to get the rated performances is usually missing, as well as the corresponding ambient temperature Ta, and, last but not least, details about the specific computational test workload.  

For instance, an [[Intel]]’s general support page states briefly that the TDP refers to "the power consumption under the maximum theoretical load".<ref>{{Cite web |title=Thermal Design Power (TDP) in Intel&reg; Processors |url=https://www.intel.com/content/www/us/en/support/articles/000055611/processors.html |access-date=2025-01-15 |website=Intel |language=en}}</ref> Here they also inform that starting from the 12th generation of their [[CPU]]s the term ''thermal design power (TDP)'' has been replaced with ''processor base power (PBP)''.<ref>{{Cite web |last=Aufranc (CNXSoft) |first=Jean-Luc |date=2022-01-08 |title=TDP (Thermal Design Power) vs PBP (Processor Base Power) - Are there differences? - CNX Software |url=https://www.cnx-software.com/2022/01/08/tdp-vs-pbp-thermal-design-power-vs-pbp-processor-base-power-differences/ |access-date=2025-01-15 |website=CNX Software - Embedded Systems News |language=en-US}}</ref> In a support page dedicated to the [[Core i7]]-7700 processor, [[Intel]] defines the TDP as the maximum amount of heat that a processor can produce when running real life applications,<ref>{{Cite web |title=Does Thermal Design Power Mean Real Power Consumption? |url=https://www.intel.com/content/www/us/en/support/articles/000031072/processors/intel-core-processors.html |access-date=2025-01-15 |website=Intel |language=en}} </ref> without telling what these "real life applications" are. Another example: in a 2011 white paper where the [[Xeon]] processors are compared with [[AMD]]’s competing devices, [[Intel]] defines TDP as the upper point of the thermal profile measured at maximum case temperature, but without specifying what this temperature should be (nor the computing load). <ref>https://www.intel.com/content/dam/doc/white-paper/resources-xeon-measuring-processor-power-paper.pdf  Measuring Processor Power – TDP vs. ACP</ref>
It is important to note that all these definitions imply that the [[CPU]] is running at the base clock rate (non-turbo). 

In conclusion:

:*Comparing the TDP between devices of different manufacturers is not very meaningful. 

:*The selection of a [[heat sink]] may end up with overheating (and [[CPU]] reduced performances) or overcooling (oversized, expensive [[heat sink]] ), depending if one chooses a too high or a too low case temperature Tc (respectively with a too low or too high ambient temperature Ta), or if the [[CPU]] operates with different computational loads.

:*A possible approach to ensure a long life of a [[CPU]] is to ask the manufacturer the recommended maximum case temperature Tc and then to oversize the cooling system. For instance, a safety margin taking into account some turbo overclocking could consider a thermal power that is 1.5 times the rated TDP. In any case, the lower is the silicon [[junction temperature]], the longer will be the lifespan of the device, according to an acceleration factor very roughly expressed by means of the [[Arrhenius equation]].<ref> https://www.ti.com/lit/an/sprabx4b/sprabx4b.pdf?ts=1736495510813 Calculating Useful Lifetimes of Embedded Processors</ref><ref>{{Cite web |last=Wilcoxon |first=Ross |date=2017-08-18 |title=Does a 10°C Increase in Temperature Really Reduce the Life of Electronics by Half? |url=https://www.electronics-cooling.com/2017/08/10c-increase-temperature-really-reduce-life-electronics-half/ |access-date=2025-01-15 |website=Electronics Cooling |language=en-US}}</ref><ref> {{Cite web |last=Johnstone |first=Caitlin |date=2019-05-30 |title=Device Reliability - How Temperature Affects Mean Time to Failure |url=https://jetcool.com/post/semiconductor-lifetime-how-temperature-affects-mean-time-to-failure-device-reliability/ |access-date=2025-01-15 |website=JetCool Microconvective Liquid Cooling |language=en-US}}</ref>