# Thermal design power

Last updated

The thermal design power (TDP), sometimes called thermal design point, is the maximum amount of heat generated by a computer chip or component (often a CPU, GPU or system on a chip) that the cooling system in a computer is designed to dissipate under any workload.

In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter. The mechanisms include conduction, through direct contact of immobile bodies, or through a wall or barrier that is impermeable to matter; or radiation between separated bodies; or isochoric mechanical work done by the surroundings on the system of interest; or Joule heating by an electric current driven through the system of interest by an external system; or a combination of these. When there is a suitable path between two systems with different temperatures, heat transfer occurs necessarily, immediately, and spontaneously from the hotter to the colder system. Thermal conduction occurs by the stochastic (random) motion of microscopic particles. In contrast, thermodynamic work is defined by mechanisms that act macroscopically and directly on the system's whole-body state variables; for example, change of the system's volume through a piston's motion with externally measurable force; or change of the system's internal electric polarization through an externally measurable change in electric field. The definition of heat transfer does not require that the process be in any sense smooth. For example, a bolt of lightning may transfer heat to a body.

A system on a chip or system on chip is an integrated circuit that integrates all components of a computer or other electronic system. These components typically include a central processing unit (CPU), memory, input/output ports and secondary storage – all on a single substrate or microchip, the size of a coin. It may contain digital, analog, mixed-signal, and often radio frequency signal processing functions, depending on the application. As they are integrated on a single substrate, SoCs consume much less power and take up much less area than multi-chip designs with equivalent functionality. Because of this, SoCs are very common in the mobile computing and edge computing markets. Systems on chip are commonly used in embedded systems and the Internet of Things.

Computer cooling is required to remove the waste heat produced by computer components, to keep components within permissible operating temperature limits. Components that are susceptible to temporary malfunction or permanent failure if overheated include integrated circuits such as central processing units (CPUs), chipset, graphics cards, and hard disk drives.

## Contents

The TDP is typically not the largest amount of heat the CPU could ever generate (peak power), such as by running a power virus, but rather the maximum amount of heat that it would generate when running "real applications". This ensures the computer will be able to handle essentially all applications without exceeding its thermal envelope, or requiring a cooling system for the maximum theoretical power (which would cost more but in favor of extra headroom for processing power). [1]

In electrical engineering and mechanical engineering, the power rating of equipment is the highest power input allowed to flow through particular equipment. According to the particular discipline, the term "power" may refer to the electrical or mechanical power. A power rating can also involve average and maximum power, which may vary depending on the kind of equipment and its application.

A power virus is a computer program that executes specific machine code to reach the maximum CPU power dissipation. Computer cooling apparatus are designed to dissipate power up to the thermal design power, rather than maximum power, and a power virus could cause the system to overheat if it does not have logic to stop the processor. This may cause permanent physical damage. Power viruses can be malicious, but are often suites of test software used for integration testing and thermal testing of computer components during the design phase of a product, or for product benchmarking.

Application software is software designed to perform a group of coordinated functions, tasks, or activities for the benefit of the user. Examples of an application include a word processor, a spreadsheet, an accounting application, a web browser, an email client, a media player, a file viewer, an aeronautical flight simulator, a console game or a photo editor. The collective noun application software refers to all applications collectively. This contrasts with system software, which is mainly involved with running the computer.

Some sources state that the peak power for a microprocessor is usually 1.5 times the TDP rating. [2] However, the TDP is a conventional figure while its measurement methodology has been the subject of controversy. In particular, until around 2006 AMD used to report the maximum power draw of its processors as TDP, but Intel changed this practice with the introduction of its Conroe family of processors. [3]

Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California, in the Silicon Valley. It is the world's second largest and second highest valued semiconductor chip manufacturer based on revenue after being overtaken by Samsung Electronics, and is the inventor of the x86 series of microprocessors, the processors found in most personal computers (PCs). Intel ranked No. 46 in the 2018 Fortune 500 list of the largest United States corporations by total revenue.

Conroe is the code name for many Intel processors sold as Core 2 Duo, Xeon, Pentium Dual-Core and Celeron. It was the first desktop processor to be based on the Core microarchitecture, replacing the NetBurst microarchitecture based Cedar Mill processor. It has product code 80557, which is shared with Allendale and Conroe-L that are very similar but have a smaller L2 cache. Conroe-L has only one processor core and a new CPUID model. The mobile version of Conroe is Merom, the dual-socket server version is Woodcrest, and the quad-core desktop version is Kentsfield. Conroe was replaced by the 45 nm Wolfdale processor.

A similar but more recent controversy has involved the power TDP measurements of some Ivy Bridge Y-series processors, with which Intel has introduced a new metric called scenario design power (SDP). [4] [5]

Ivy Bridge is the codename for the "third generation" of the Intel Core processors. Ivy Bridge is a die shrink to 22 nanometer manufacturing process based on the 32 nanometer Sandy Bridge - see tick–tock model. The name is also applied more broadly to the 22 nm die shrink of the Sandy Bridge microarchitecture based on FinFET ("3D") Tri-Gate transistors, which is also used in the Xeon and Core i7 Ivy Bridge-EX (Ivytown), Ivy Bridge-EP and Ivy Bridge-E microprocessors released in 2013.

## Overview

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. [6] 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 heatsink.

For example, a laptop's CPU cooling system may be designed for a 20  W TDP, which means that it can dissipate up to 20 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. forced convection) such as a fan, or any of the three passive cooling methods: convection, thermal radiation or conduction. Typically, a combination of these methods is used.

A laptop computer is a small, portable personal computer (PC) with a "clamshell" form factor, typically having a thin LCD or LED computer screen mounted on the inside of the upper lid of the clamshell and an alphanumeric keyboard on the inside of the lower lid. The clamshell is opened up to use the computer. Laptops are folded shut for transportation, and thus are suitable for mobile use. Its name comes from lap, as it was deemed to be placed on a person's lap when being used. Although originally there was a distinction between laptops and notebooks, as of 2014, there is often no longer any difference. Laptops are commonly used in a variety of settings, such as at work, in education, for playing games, Internet surfing, for personal multimedia, and general home computer use.

The watt is a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer. In dimensional analysis, power is described by .

Junction temperature, short for transistor junction temperature, is the highest operating temperature of the actual semiconductor in an electronic device. In operation, it is higher than case temperature and the temperature of the part's exterior. The difference is equal to the amount of heat transferred from the junction to case multiplied by the junction-to-case thermal resistance.

Since safety margins and the definition of what constitutes a real application vary among manufacturers, TDP values between different manufacturers cannot be accurately compared. For example, while a processor with a TDP of 100 W will almost certainly use more power at full load than a processor with a 10 W TDP from the same manufacturer, it may or may not use more power than a processor from a different manufacturer that has a 90 W TDP. 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.

The dynamic power consumed by a switching circuit is approximately proportional to the square of the voltage: [7]

${\displaystyle P=CV^{2}f}$

where C is capacitance, f is frequency, and V is voltage.

## Variable TDP

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

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 January 2014) and AMD processors (as of June 2012) 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. [8] :6972 [9] [10]

Intel processors that support cTDP provide three operating modes: [8] :7172

• Nominal TDP  this is the processor's rated frequency and TDP.
• cTDP down  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  when extra cooling is available, this mode specifies a higher TDP and higher guaranteed frequency versus the nominal mode.

For example, some of the mobile Haswell processors support cTDP up, cTDP down, or both modes. [11] As another example, some of the AMD Opteron processors and Kaveri APUs can be configured for lower TDP values. [9] [10] [12] IBM's POWER8 processor implements a similar power capping functionality through its embedded on-chip controller (OCC). [13]

### Scenario design power

Intel's description of Scenario Design Power (SDP): "SDP is an additional thermal reference point meant to represent thermally relevant device usage in real-world environmental scenarios. It balances performance and power requirements across system workloads to represent real-world power usage." [14]

Scenario design power (SDP) is not an additional power state of a processor. The SDP only states the average power consumption of a processor using a certain mix of benchmark programs to simulate "real-world" scenarios". [4] [15] [16] For example, Y-series (extreme-low power) mobile Haswell processor show the difference between TDP and SDP. [14]

## Related Research Articles

Opteron is AMD's x86 former server and workstation processor line, and was the first processor which supported the AMD64 instruction set architecture. It was released on April 22, 2003, with the SledgeHammer core (K8) and was intended to compete in the server and workstation markets, particularly in the same segment as the Intel Xeon processor. Processors based on the AMD K10 microarchitecture were announced on September 10, 2007, featuring a new quad-core configuration. The most-recently released Opteron CPUs are the Piledriver-based Opteron 4300 and 6300 series processors, codenamed "Seoul" and "Abu Dhabi" respectively. In January 2016, the first ARMv8-A based Opteron SoC was released.

In computing, overclocking is the practice of increasing the clock frequency of a computer to exceed that certified by the manufacturer. Commonly operating voltage is also increased to maintain a component's operational stability at accelerated speeds. Semiconductor devices operated at higher frequencies and voltages increase power consumption and heat. An overclocked device may be unreliable or fail completely if the additional heat load is not removed or power delivery components cannot meet increased power demands. Many device warranties state that overclocking and/or over-specification voids any warranty.

The Athlon 64 is an eighth-generation, AMD64-architecture microprocessor produced by AMD, released on September 23, 2003. It is the third processor to bear the name Athlon, and the immediate successor to the Athlon XP. The second processor to implement AMD64 architecture and the first 64-bit processor targeted at the average consumer, it was AMD's primary consumer microprocessor, and competes primarily with Intel's Pentium 4, especially the "Prescott" and "Cedar Mill" core revisions. It is AMD's first K8, eighth-generation processor core for desktop and mobile computers. Despite being natively 64-bit, the AMD64 architecture is backward-compatible with 32-bit x86 instructions. Athlon 64s have been produced for Socket 754, Socket 939, Socket 940 and Socket AM2. The line was succeeded by the dual-core Athlon 64 X2 and Athlon X2 lines.

Central processing unit power dissipation or CPU power dissipation is the process in which central processing units (CPUs) consume electrical energy, and dissipate this energy in the form of heat due to the resistance in the electronic circuits.

Underclocking, also known as downclocking, is modifying a computer or electronic circuit's timing settings to run at a lower clock rate than is specified. Underclocking is used to reduce a computer's power consumption, increase battery life, reduce heat emission, and it may also increase the system's stability and compatibility. Underclocking may be implemented by the factory, but many computers and components may be underclocked by the end user.

Power management is a feature of some electrical appliances, especially copiers, computers, GPUs and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power state when inactive. In computing this is known as PC power management and is built around a standard called ACPI. This supersedes APM. All recent (consumer) computers have ACPI support.

The Pentium D brand refers to two series of desktop dual-core 64-bit x86-64 microprocessors with the NetBurst microarchitecture, which is the dual-core variant of Pentium 4 "Prescott" manufactured by Intel. Each CPU comprised two dies glued together, each containing a single core, residing next to each other on a multi-chip module package. The brand's first processor, codenamed Smithfield, was released by Intel on May 25, 2005. Nine months later, Intel introduced its successor, codenamed Presler, but without offering significant upgrades in design, still resulting in relatively high power consumption. By 2004, the NetBurst processors reached a clock speed barrier at 3.8 GHz due to a thermal limit exemplified by the Presler's 130 watt thermal design power. The future belonged to more energy efficient and slower clocked dual-core CPUs on a single die instead of two. The final shipment date of the dual die Presler chips was August 8, 2008, which marked the end of the Pentium D brand and also the NetBurst microarchitecture.

A voltage regulator module (VRM), sometimes called processor power module (PPM), is a buck converter that provides a microprocessor the appropriate supply voltage, converting +5 V or +12 V to a much lower voltage required by the CPU, allowing processors with different supply voltage to be mounted on the same motherboard.

AMD Cool'n'Quiet is a CPU dynamic frequency scaling and power saving technology introduced by AMD with its Athlon 64 processor line. It works by reducing the processor's clock rate and voltage when the processor is idle. The aim of this technology is to reduce overall power consumption and lower heat generation, allowing for slower cooling fan operation. The objectives of cooler and quieter result in the name Cool'n'Quiet. The technology is similar to Intel's SpeedStep and AMD's own PowerNow!, which were developed with the aim of increasing laptop battery life by reducing power consumption.

The AMD Family 10h, or K10, is a microprocessor microarchitecture by AMD based on the K8 microarchitecture. Though there were once reports that the K10 had been canceled, the first third-generation Opteron products for servers were launched on September 10, 2007, with the Phenom processors for desktops following and launching on November 11, 2007 as the immediate successors to the K8 series of processors.

The AMD Accelerated Processing Unit (APU), formerly known as Fusion, is the marketing term for a series of 64-bit microprocessors from Advanced Micro Devices (AMD), designed to act as a central processing unit (CPU) and graphics processing unit (GPU) on a single die.

AMD Turion is the brand name AMD applies to its x86-64 low-power consumption (mobile) processors codenamed K8L. The Turion 64 and Turion 64 X2/Ultra processors compete with Intel's mobile processors, initially the Pentium M and the Intel Core and Intel Core 2 processors.

The average CPU power (ACP), is a scheme to characterize power consumption of new central processing units under "average" daily usage, especially server processors, the rating scheme is defined by Advanced Micro Devices (AMD) for use in its line of processors based on the K10 microarchitecture. This rating is similar to Intel's thermal design power (TDP) used with Pentium and Core 2 processors, measuring the energy consumption of high workloads, which in numbers are slightly lower than the TDP value of the same processor.

Dynamic frequency scaling is a technique in computer architecture whereby the frequency of a microprocessor can be automatically adjusted "on the fly" depending on the actual needs, to conserve power and reduce the amount of heat generated by the chip. Dynamic frequency scaling helps preserve battery on mobile devices and decrease cooling cost and noise on quiet computing settings, or can be useful as a security measure for overheated systems. Dynamic frequency scaling is used in all ranges of computing systems, ranging from mobile systems to data centers to reduce the power at the times of low workload.

Haswell is the codename for a processor microarchitecture developed by Intel as the "fourth-generation core" successor to the Ivy Bridge microarchitecture. Intel officially announced CPUs based on this microarchitecture on June 4, 2013, at Computex Taipei 2013, while a working Haswell chip was demonstrated at the 2011 Intel Developer Forum. With Haswell, which uses a 22 nm process, Intel also introduced low-power processors designed for convertible or "hybrid" ultrabooks, designated by the "Y" suffix.

Broadwell is Intel's codename for the 14 nanometer die shrink of its Haswell microarchitecture. It is a "tick" in Intel's tick–tock principle as the next step in semiconductor fabrication. Like some of the previous tick-tock iterations, Broadwell did not completely replace the full range of CPUs from the previous microarchitecture (Haswell), as there were no low-end desktop CPUs based on Broadwell.

AMD Piledriver Family 15h is a microarchitecture developed by AMD as the second-generation successor to Bulldozer. It targets desktop, mobile and server markets. It is used for the AMD Accelerated Processing Unit, AMD FX, and the Opteron line of processors.

Kaby Lake is an Intel codename for a processor microarchitecture Intel announced on August 30, 2016. Like the preceding Skylake, Kaby Lake is produced using a 14 nanometer manufacturing process technology. Breaking with Intel's previous "tick–tock" manufacturing and design model, Kaby Lake represents the optimized step of the newer "process-architecture-optimization" model. Kaby Lake began shipping to manufacturers and OEMs in the second quarter of 2016, and mobile chips have started shipping while Kaby Lake (desktop) chips were officially launched in January 2017.

AMD Turbo Core a.k.a. AMD Core Performance Boost (CPB) is a technology implemented by AMD that allows the processor to dynamically adjust and control the processor operating frequency in certain versions of its processors which allows for increased performance when needed while maintaining lower power and thermal parameters during normal operation. AMD Turbo Core technology has been implemented beginning with the Phenom II X6 microprocessors based on the AMD K10 microarchitecture. AMD Turbo Core is available with some AMD A-Series accelerated processing units.

## References

1. "The technical details behind Intel's 7 Watt Ivy Bridge CPUs". arstechnica.com. 2013-01-14. Retrieved 2013-01-14. In Intel's case, a specified chip's TDP has less to do with the amount of power a chip needs to use (or can use) and more to do with 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.
2. John L. Hennessy; David A. Patterson (2012). Computer Architecture: A Quantitative Approach (5th ed.). Elsevier. p. 22. ISBN   978-0-12-383872-8.
3. Ou, George (2006-07-17). "Who to believe on power consumption? AMD or Intel?". ZDNet. Retrieved 2014-02-11.
4. Anand Lal Shimpi (2013-01-14). "Intel Brings Core Down to 7W, Introduces a New Power Rating to Get There: Y-Series SKUs Demystified". anandtech.com. Retrieved 2014-02-11.
5. Crothers, Brooke (2013-01-09). "Intel responds to cooked power efficiency claims". ces.cnet.com. Retrieved 2014-02-11.
6. Stanislav Garmatyuk (2004-03-26). "Testing Thermal Throttling in Pentium 4 CPUs with Northwood and Prescott cores". ixbtlabs.com. Retrieved 2013-12-21.
7. "Enhanced Intel SpeedStep Technology for the Intel Pentium M Processor (White Paper)" (PDF). Intel Corporation. March 2004. Archived from the original (PDF) on 2015-08-12. Retrieved 2013-12-21.
8. "4th Generation Intel Core processor based on Mobile M-Processor and H-Processor Lines Datasheet, Volume 1 of 2" (PDF). Intel. December 2013. Retrieved 2013-12-22. Configurable TDP (cTDP) and Low-Power Mode (LPM) form a design vector where the processor behavior and package TDP are dynamically adjusted to a desired system performance and power envelope. [...] With cTDP, the processor is now capable of altering the maximum sustained power with an alternate guaranteed frequency. Configurable TDP allows operation in situations where extra cooling is available or situations where a cooler and quieter mode of operation is desired.
9. Michael Larabel (2014-01-22). "Testing Out The Configurable TDP On AMD's Kaveri". Phoronix . Retrieved 2014-08-31.
10. "AMD Opteron 4200 Series Processor Quick Reference Guide" (PDF). Advanced Micro Devices. June 2012. Retrieved 2014-08-31.
11. "Sony Vaio Duo 13 Review". mobiletechreview.com. 2013-07-22. Retrieved 2014-02-11.
12. Michael Larabel (2014-08-13). "Trying The Configurable 45 Watt TDP With AMD's A10-7800 / A6-7400K". Phoronix . Retrieved 2014-08-31.
13. Todd Rosedahl (2014-12-20). "OCC Firmware Code is Now Open Source". openpowerfoundation.org. Retrieved 2014-12-27.
14. "Intel Core i7-4610Y Processor (4M Cache, up to 2.90 GHz)". Intel . Retrieved 2014-02-11.
15. "The technical details behind Intel's 7 Watt Ivy Bridge CPUs". Ars Technica. 2013-01-14. Retrieved 2013-12-22. If the CPU needs to work hard for an extended period of time and the laptop gets warmer, it will slowly ramp down its speed until it's operating at its stated TDP. [...] There are two OEM-configurable "power level" states that define how quick the CPU can be in these situations: PL2 tells the processor how much power it's allowed to use when it needs a short burst of speed, and PL1 defines how quickly the processor can run under sustained load. [...] This is at the heart of what Intel is doing with the Y-series processors: their maximum TDP has been lowered four watts, from 17 to 13. Intel is also validating them for use at two lower PL1 values: 10 watts and 7 watts. This is where the marketing we discussed earlier comes in—rather than keeping these values under the covers as it has so far been content to do, Intel has taken that lowest value, put it on its product pages, and called it SDP.
16. "4th Generation Intel Core processor based on Mobile U-Processor and Y-Processor Lines Datasheet, Volume 1 of 2" (PDF). Intel. December 2013. Retrieved 2013-12-22.