View source for Thermal design power

{{Short description|Amount of heat a computer's cooling system must dissipate}}
{{About|the thermal design envelope of microprocessors|the general concept|power rating}}

[[File:AMD_heatsink_and_fan.jpg | thumb | right | alt=Heatsink made of aluminum fins and core mounted on a motherboard, with an approximately half hand-sized fan attached on the top of it. The aluminum core of the heatsink contacts the 40x40mm CPU surface underneath it, taking heat away through thermal conduction. This heatsink is designed with the cooling capacity matching the CPU’s TDP | Heatsink mounted on a motherboard, cooling the CPU underneath it. This heatsink is designed with the cooling capacity matching the CPU’s TDP.]]
'''Thermal Design Power''' ('''TDP'''), also known as '''thermal design point''', is the maximum amount of [[heat]] that a computer component (like a [[CPU]], [[GPU]] or [[system on a chip]]) can generate and that its [[computer cooling|cooling system]] is designed to [[dissipation|dissipate]] during normal operation at a non-turbo clock rate (base frequency).

Some sources state that the peak [[power rating]] for a microprocessor is usually 1.5 times the TDP rating.<ref name="HennessyPatterson2012">{{ cite book | author1 = John L. Hennessy |author2 = David A. Patterson | title = Computer Architecture: A Quantitative Approach | url = https://books.google.com/books?id=v3-1hVwHnHwC&pg=PA22 | year = 2012 | publisher = Elsevier | isbn = 978-0-12-383872-8 | page = 22 | edition = 5th }}</ref>

== Calculation ==
{{See also|CPU power dissipation}}
{| class="wikitable floatright"
|+ ACP compared to TDP<ref>John Fruehe. [http://www.amdzone.com/phpbb3/viewtopic.php?f=52&t=136664&p=164919#p164919 "Istanbul EE launches today"] {{Webarchive|url=https://web.archive.org/web/20110728150811/http://www.amdzone.com/phpbb3/viewtopic.php?f=52&t=136664&p=164919#p164919 |date=2011-07-28 }}</ref>
|-
! style="min-width: 5em;" | ACP
! style="min-width: 5em;" | TDP
|-
| 40&nbsp;W || 60&nbsp;W
|-
| 55&nbsp;W || 79&nbsp;W
|-
| 75&nbsp;W || 115&nbsp;W
|-
| 105&nbsp;W || 137&nbsp;W
|}

The ''average CPU power'' (ACP) is the power consumption of [[central processing unit]]s, especially [[server computer|server]] processors, under "average" daily usage as defined by [[Advanced Micro Devices]] (AMD) for use in its line of processors based on the [[AMD K10|K10]] microarchitecture ([[Opteron#Micro-architecture update|Opteron 8300 and 2300 series]] processors). Intel's thermal design power (TDP), used for Pentium and Core 2 processors, measures the energy consumption under high workload; it is numerically somewhat higher than the "average" ACP rating of the same processor.

According to AMD the ACP rating includes the power consumption when running several benchmarks, including [[TPC-C]], [[SPEC#Current|SPECcpu2006]], [[SPEC#Current|SPECjbb2005]] and STREAM Benchmark<ref>{{cite web |url=https://www.cs.virginia.edu/stream/|title=Memory bandwidth: Stream benchmark performance results |work=virginia.edu}}</ref> (memory bandwidth),<ref>{{Cite web |title=AMD's Quad-Core Barcelona: Defending New Territory |last=de Gelas |first=Johan|website=AnandTech |date=10 September 2007 |url= https://www.anandtech.com/show/2322/2}}</ref>
<ref>{{Cite web|url=http://www.dailytech.com/AMD+Unveils+Barcelona+Architecture/article6299.htm|date=7 September 2007|archive-url=
https://web.archive.org/web/20071027183549/http://www.dailytech.com/AMD+Unveils+Barcelona+Architecture/article6299.htm|archive-date=27 October 2007|title=AMD Unveils "Barcelona" Architecture|last1=Huynh|first1=Anh T.|last2=Kubicki|first2=Kristopher |website=DailyTech}}</ref><ref>[https://web.archive.org/web/20171218005536/http://images.dailytech.com/nimage/5925_large_amd_explains_acp.png DailyTech - Introducing Average CPU Power], September 2007</ref> which AMD said is an appropriate method of power consumption measurement for [[data center]]s and server-intensive workload environments. AMD said that the ACP and TDP values of the processors will both be stated and do not replace one another. ''Barcelona'' and later server processors have the two power figures.

The TDP of a CPU has been underestimated in some cases, leading to certain real applications (typically strenuous, such as video encoding or games) causing the CPU to exceed its specified TDP and resulting in overloading the computer's cooling system.  In this case, CPUs either cause a system failure (a "therm-trip") or throttle their speed down.<ref>{{cite web | url = http://ixbtlabs.com/articles2/p4-throttling/ | title = Testing Thermal Throttling in Pentium 4 CPUs with Northwood and Prescott cores | date = 2004-03-26 | access-date = 2013-12-21 | author = Stanislav Garmatyuk | website = ixbtlabs.com }}</ref>  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.

For example, a [[laptop]]'s CPU cooling system may be designed for a 20&nbsp;[[Watt|W]] TDP, which means that it can dissipate up to 20&nbsp;watts of heat without exceeding the maximum [[junction temperature]] for the laptop's CPU. A cooling system can do this using an active cooling method (e.g. conduction coupled with forced convection) such as a [[heat sink]] with a [[Computer fan|fan]], or any of the two passive cooling methods: [[thermal radiation]] or [[Conduction (heat)|conduction]]. Typically, a combination of these methods is used.

Since safety margins and the definition of what constitutes a real application vary among manufacturers, TDP values between different manufacturers cannot be accurately compared (a processor with a TDP of, for example, 100&nbsp;W will almost certainly use more power at full load than processors with a fraction of said TDP, and very probably more than processors with lower TDP from the same manufacturer, but it may or may not use more power than a processor from a different manufacturer with a not excessively lower TDP, such as 90&nbsp;W). Additionally, TDPs are often specified for families of processors, with the low-end models usually using significantly less power than those at the high end of the family.

Until around 2006 [[AMD]] used to report the maximum power draw of its processors as TDP. [[Intel]] changed this practice with the introduction of its [[Conroe (microprocessor)|Conroe]] family of processors.<ref>{{cite web | last = Ou | first = George | url = https://www.zdnet.com/article/who-to-believe-on-power-consumption-amd-or-intel/ | title = Who to believe on power consumption? AMD or Intel? | publisher = ZDNet | date = 2006-07-17 | access-date = 2014-02-11 }}</ref> Intel calculates a specified chip's TDP according to the amount of power the computer's fan and heatsink need to be able to dissipate while the chip is under sustained load. 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.<ref>{{ cite web | url = https://arstechnica.com/gadgets/2013/01/the-technical-details-behind-intels-7-watt-ivy-bridge-cpus/ | title = The technical details behind Intel's 7 Watt Ivy Bridge CPUs | date = 2013-01-14 | access-date = 2013-01-14 | publisher = arstechnica.com }}</ref> In particular, Intel's measurement also does not fully take into account [[Intel Turbo Boost]] due to the default time limits, while AMD does because [[AMD Turbo Core]] always tries to push for the maximum power.<ref>{{cite web |author1=Linus Tech Tips |title=Who REALLY Runs Hotter? AMD (3800X) vs Intel (i9-9900K) |url=https://www.youtube.com/watch?v=6u4ew6IT4Vo |website=YouTube |date=Sep 16, 2019 }}</ref>

== Alternatives ==

TDP specifications for some processors may allow them to work under multiple different power levels, depending on the usage scenario, available cooling capacities and desired power consumption.  Technologies that provide such variable TDPs include [[Intel]]'s ''configurable TDP'' (cTDP) and ''scenario design power'' (SDP), and [[AMD]]'s ''TDP power cap''.

''Configurable TDP'' (''cTDP''), also known as ''programmable TDP'' or ''TDP power cap'', is an operating mode of later generations of Intel mobile processors ({{As of|2014|January|lc=yes}}) and AMD processors ({{As of|2012|June|lc=yes}}) that allows adjustments in their TDP values.  By modifying the processor behavior and its performance levels, power consumption of a processor can be changed altering its TDP at the same time.  That way, a processor can operate at higher or lower performance levels, depending on the available cooling capacities and desired power consumption.<ref name="intel-mh-lines">{{ cite web | url = http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/4th-gen-core-family-mobile-m-h-processor-lines-vol-1-datasheet.pdf | title = 4th Generation Intel Core processor based on Mobile M-Processor and H-Processor Lines Datasheet, Volume 1 of 2 | date = December 2013 | access-date = 2013-12-22 | publisher = [[Intel]] }}</ref>{{rp|69–72}}<ref name="phoronix-amd-kaveri">{{ cite web | url = https://www.phoronix.com/scan.php?page=article&item=amd_kaveri_tdp&num=1 | title = Testing Out The Configurable TDP On AMD's Kaveri | date = 2014-01-22 | access-date = 2014-08-31 | author = Michael Larabel | publisher = [[Phoronix]] }}</ref><ref name="amd-opteron-4200">{{ cite web | url = https://www.amd.com/Documents/Opteron_4000_QRG.pdf | title = AMD Opteron 4200 Series Processor Quick Reference Guide | date = June 2012 | access-date = 2014-08-31 | publisher = [[Advanced Micro Devices]] }}</ref>

cTDP typically provide (but are not limited to) three operating modes:<ref name="intel-mh-lines" />{{rp|71–72}}

* ''Nominal TDP''{{snd}} the processor's rated frequency and TDP.
* ''cTDP down''{{snd}} when a cooler or quieter mode of operation is desired, this mode specifies a lower TDP and lower guaranteed frequency versus the nominal mode.
* ''cTDP up''{{snd}} when extra cooling is available, this mode specifies a higher TDP and higher guaranteed frequency versus the nominal mode.

For example, some of the [[Haswell (microarchitecture)#MOBILE|mobile Haswell]] processors support cTDP up, cTDP down, or both modes.<ref>{{Cite web | url = http://www.mobiletechreview.com/notebooks/Sony-Vaio-Duo-13.htm | title = Sony Vaio Duo 13 Review | date = 2013-07-22 | access-date = 2014-02-11 | website = mobiletechreview.com }}</ref>  As another example, some of the AMD [[Opteron]] processors and [[AMD Kaveri|Kaveri]] [[AMD Accelerated Processing Unit|APUs]] can be configured for lower TDP values.<ref name="amd-opteron-4200" />  IBM's [[POWER8]] processor implements a similar power capping functionality through its embedded [[POWER8 on-chip controller|on-chip controller]] (OCC).<ref>{{Cite web | url = http://openpowerfoundation.org/press-releases/occ-firmware-code-is-now-open-source/ | title = OCC Firmware Code is Now Open Source | date = 2014-12-20 | access-date = 2014-12-27 | author = Todd Rosedahl | website = openpowerfoundation.org }}</ref>

Intel introduced ''scenario design power'' (SDP) for some low power Y-series processors since 2013.<ref name="anandtech-6655">{{Cite web |author=Anand Lal Shimpi |date=2013-01-14 |title=Intel Brings Core Down to 7W, Introduces a New Power Rating to Get There: Y-Series SKUs Demystified |url=http://www.anandtech.com/show/6655/intel-brings-core-down-to-7w-introduces-a-new-power-rating-to-get-there-yseries-skus-demystified |access-date=2014-02-11 |publisher=anandtech.com}}</ref><ref>{{cite web |last=Crothers |first=Brooke |date=2013-01-09 |title=Intel responds to cooked power efficiency claims |url=http://ces.cnet.com/8301-34435_1-57563024/intel-responds-to-cooked-power-efficiency-claims/ |access-date=2014-02-11 |publisher=ces.cnet.com}}</ref> It is described as "an additional thermal reference point meant to represent thermally relevant device usage in real-world environmental scenarios."<ref name=":0">{{cite web |title=Intel Core i7-4610Y Processor (4M Cache, up to 2.90 GHz) |url=http://ark.intel.com/products/76618 |access-date=2014-02-11 |publisher=[[Intel]]}}</ref>{{Promotional source|date=December 2024}} As a power rating, SDP is not an additional power state of a processor; it states the average power consumption of a processor using a certain mix of benchmark programs to simulate "real-world" scenarios.<ref name="anandtech-6655" /><ref>{{cite web | url = https://arstechnica.com/gadgets/2013/01/the-technical-details-behind-intels-7-watt-ivy-bridge-cpus/ | title = The technical details behind Intel's 7 Watt Ivy Bridge CPUs | date = 2013-01-14 | access-date = 2013-12-22 | publisher = Ars Technica }}</ref><ref>{{cite web | url = http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/4th-gen-core-family-mobile-u-y-processor-lines-vol-1-datasheet.pdf | title = 4th Generation Intel Core processor based on Mobile U-Processor and Y-Processor Lines Datasheet, Volume 1 of 2 | date = December 2013 | access-date = 2013-12-22 | publisher = [[Intel]] }}</ref>

== Ambiguities of the Thermal Design Power parameter==

As some authors and users have observed, the Thermal Design Power (TDP) rating is an ambiguous parameter.<ref>{{Cite web |title=Thermal design power |url=https://linuxreviews.org/Thermal_design_power |access-date=2025-01-15 |website=LinuxReviews |language=en}}</ref><ref>{{Cite web |last=Tarara |first=Arne |title=TDP and ACP for energy estimation in processors |url=https://www.green-coding.io/blog/tdp-and-acp/ |access-date=2025-01-15 |website=www.green-coding.io |language=en}}</ref><ref>{{Cite web |last= |first= |title=Cooling for modern CPUs |url=https://www.bequiet.com/en/insidebequiet/5017 |access-date=2025-01-15 |website=be quiet! |language=en}}</ref><ref>{{Cite web |title=Noctua’s Standardised Performance Rating (NSPR) and compatibility classification for CPU coolers |url=https://noctua.at/en/noctua-standardised-performance-rating |access-date=2025-01-15 |website=noctua.at}}</ref><ref name="TDP_Definitions">{{Cite web |title=AMD Ryzen TDP Explained: Deep-Dive on TDP Definitions & What Cooler Manufacturers Think {{!}} GamersNexus |url=https://gamersnexus.net/guides/3525-amd-ryzen-tdp-explained-deep-dive-cooler-manufacturer-opinions |access-date=2025-01-15 |website=gamersnexus.net |language=en}}</ref><ref name="Cooling_and_Efficiency">{{Cite web |last=Lagergren |first=Evan |date=2024-09-19 |title=Power Draw, Cooling, and Efficiency: AMD Ryzen 9000 Series Processors |url=https://www.pugetsystems.com/labs/articles/power-draw-cooling-and-efficiency-amd-ryzen-9000-series-processors/?srsltid=AfmBOooQlLsZaxtOMnCD84eLvA6PdlSYr4kN7tOi-1UTDxXuihqvq--b |access-date=2025-01-15 |website=Puget Systems |language=en-US}} </ref> 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. 

=== Thermal Management fundamentals ===

To better understand the problem we must remember the basic concepts underlying [[Thermal management (electronics)|Thermal management]] and [[Computer cooling]]. <ref name=Cooling_and_Efficiency /> Let’s consider the [[thermal conduction]] path from the [[CPU]] case to the ambient air through a [[Heat sink]], with:

:Pd  ([[Watt]]) = Thermal [[Electric power|power]] generated by a [[CPU]] and to be dissipated into the ambient through a suitable [[Heat sink]]. It corresponds to the total power drain from the direct current supply rails of the [[CPU]].
:Rca ([[°C]]/W) = [[Thermal resistance]] of the [[Heat sink]], between the case of the [[CPU]] and the ambient air.
:Tc  ([[°C]]) 	= Maximum allowed temperature of the [[CPU]]'s case (ensuring full performances).
:Ta  ([[°C]]) 	= Maximum expected ambient temperature at the inlet of the [[Heat sink]] fan.

All these parameters are linked together by the following [[equation]]:

:<math>(Tc-Ta)=Pd \cdot Rca </math>

Hence, once we know the thermal power to be dissipated (Pd), the maximum allowed case temperature (Tc) of the [[CPU]] and the maximum expected ambient temperature (Ta) of the air entering the cooling fans, we can determine the fundamental characteristics of the required [[Heat sink]], i.e. its thermal resistance Rca, as:

:<math> Rca=\frac {(Tc-Ta)}{Pd} </math>  

This equation can be rearranged by writing 

:<math> Pd=\frac{(Tc-Ta)}{ Rca} </math> 

where in Pd can replaced by the Thermal Design Power (TDP).

Note that the heat dissipation path going from the [[CPU]] to the ambient air flowing through the printed circuit of the motherboard has a thermal resistance that is orders of magnitude greater than the one of the [[Heat sink]], therefore it can be neglected in these computations.

=== 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>

=== Some disclosed details of [[AMD]]’s Thermal Design Power (TDP)===

In October 2019, the GamersNexus  Hardware Guides<ref name=TDP_Definitions /><ref>{{Cite AV media |url=https://www.youtube.com/watch?v=tL1F-qliSUk |title=AMD Ryzen TDP Deep-Dive & What Cooler Manufacturers Think of "TDP" |date=2019-10-14 |last=Gamers Nexus |access-date=2025-01-15 |via=YouTube}}</ref>  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 [[CPU]]s. The formula relating all these parameters, given by [[AMD]], is the usual 

:<math> TPD=(Tc-Ta)/Rca </math>  

The declared TPDs of these devices range from 65 W to 105 W; the ambient temperature considered by [[AMD]] is +42°[[C]], and the case temperatures range from +61.8 [[°C]] to +69.3[[°C]], while the case-to-ambient thermal resistances range from 0.189 to 0.420 [[°C]]/W.
== See also ==
{{Portal|Electronics}}

* [[Heat generation in integrated circuits]]
* [[Operating temperature]]
* [[Power rating]]
* [[Intel Turbo Boost]]
* [[AMD Turbo Core]]

== References ==

{{refs}}

== External links ==

* [http://www.anandtech.com/show/4481/details-on-amd-bulldozer-opterons-to-feature-configurable-tdp/2 Details on AMD Bulldozer: Opterons to Feature Configurable TDP], [[AnandTech]], July 15, 2011, by Johan De Gelas and Kristian Vättö
* [http://www.realworldtech.com/cool-x86/ Making x86 Run Cool], April 15, 2001, by Paul DeMone

[[Category:Computer engineering]]
[[Category:Heat transfer]]