9 Differences Between TDP and Power Consumption

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What are the differences between TDP and power consumption? There are different parameters in which the performance and efficiency of a CPU of a computer is measured.

One such is TDP or Thermal Design Power, of which many users have little understanding as to what it means.

It is true that the TDP rating of a CPU is meant to represent the consumption of power by it but most people do not have a full understanding regarding the relationship between the power consumption and TDP of a CPU.

As a result they often mix up the two and end up making the wrong decision.

However, TDP and power consumption are not the same and this article will tell you about the differences, whatever is available, so that you do not mix the two while determining the efficiency of your CPU.

In addition to the differences between them you will also come to know about a few other facts that will help you further in making the right choice. So, make sure that you read this article to its entirety.

The 9 Differences Between TDP and Power Consumption

Differences Between TDP and Power Consumption

1. Basic

TDP typically refers to the thermal effect due to the current flowing through the core and other types of heat energy.

On the other hand, the power consumption typically refers to the product of the current flowing through the core and the voltage of the core of the processor.

2. Meaning

TDP stands for Thermal Design Power and signifies the power consumption by the CPU when it is put to maximum theoretical load. It indicates the maximum power a system should be designed for.

Power consumption, on the other hand, is the amount of energy utilized by the CPU per unit time. Often power consumption is less than the TDP rating when a CPU is put under lower workloads.

3. Importance

The importance of the TDP rating is primarily to the manufacturers who use the value to decide what amount of power the system needs to operate and what the power of the cooling system should be that is required with it.

As for the users, it gives them a fair idea about the energy consumption and heat produced by the CPU during operation.

On the other hand, the importance of the value of power consumption is immense in digital systems.

It helps the users to determine the battery life of the mobile systems especially such as the laptop computers and cell phones which are typically limited by power consumption.

4. Unit

The unit of TDP is watts, represented as W, but the unit of power consumption is typically kilowatt-hours, represented as kWh.

5. Purpose

The purpose of TDP is to offer the system integrators and designers with a power target that will help them to select a suitable thermal solution.

Since it tells about the maximum heat the CPU will use, this is used as the fundamental indicator to determine power consumption.

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On the other hand, the purpose of power used by the CPU is to mainly run the different components and in the process a larger part of it is turned into heat due to friction while moving the electrons.

The rest of it is used for moving the fans and hard drive, lighting up the display, transferring data across the network, sending information through the wires from one place to another and more.

6. Checking

You can check the TDP of your CPU by visiting the product specification site of Intel, ark.intel.com, entering the processor number, and looking under ‘Performance.’

In order to check the power consumption of the CPU you can use one of the many online tools, selecting CPU from the drop down list and entering the details of the processor.

You can also use a third-party software application or even a power meter to know the power draw.

7. Calculation Parameters

The parameters used to calculate the TDP of a CPU are the maximum temperature it can reach, the minimum temperature for every watt that is to be dissipated, and the ambient temperature of the room.

It is also determined on the basis of the CPU frequency, process and its performance.

On the other hand, the factors that are taken into account to calculate the power draw by a CPU are the power delivery components, the memory and the system on the whole.

8. Formula

The formula used to calculate the TDP of a processor is: TDP (Watts) = (tCase (°C) – tAmbient (°C)) / (HSF Θca).

Here, tCase is the highest temperature of the die of the CPU and the internal junction of the IHS, tAmbient is the highest ambient temperature given for the heat sink fan for nominal performance, and HSF-Θca is the minimum temperature value of every watt of the heat sink.

On the other hand, the power consumption of the CPU can be calculated by using different formulas according to the given conditions such as P = IV, when P is power, I is current flowing and V is the voltage.

You can also use P=C∗V2∗F, where P is power, C is switching capacitance per clock cycle, V is voltage, and F is CPU frequency or cycles per second.

9. Requirements

The TDP value is required mainly for the cooling system that needs to know the amount of heat produced by the CPU that it needs to dissipate.

On the other hand, the requirement of power consumption of the processor is largely for the motherboard because it needs the right voltage and current.

Which is More Important – TDP or Power Consumption?

Though none of these two can be ignored completely, power consumption seems to be a bit more important.

This is because TDP is primarily focused on the cooling system but power consumption helps in a lot of other things.

Further explanation of TDP and power consumption by CPU will make things clearer for you.

The power requirements of the processor can be determined by the listed TDP value which is considered to be the stable state design target.

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However, the designers today have shifted their focus from raw performance to enhanced power efficiency.

The most important factors that affect the power requirements of a CPU are:

  • The number of cores
  • The number of threads
  • The clock speed
  • The voltage settings and
  • The manufacturing procedure in nanometers.

You can use a third party utility to determine the power consumption of Intel processors.

Though in steady conditions and under the published frequency it is the TDP value, in specific conditions such as Intel Advanced Vector Extensions or Intel AVX and turbo it can be more than the TDP value.

The time can be considered differently such as:

  • For a limited time or
  • Till the CPU hits the thermal throttle temperature or
  • Till the CPU hits the power delivery limits.

The relationship between the actual power consumption and TDP of a CPU is however not as simple as it should be.

In fact, in most of the cases the TDP rating and the actual power consumption is vastly different.

It is due to the basic difference mentioned above which is why the TDP rating given for a CPU is usually smaller than the actual power consumption of it.

This means that a CPU marked 65 watts may consume actually higher power than that.

This is why the power rating is calculated in a different and in a much better way rather than simply making a rough calculation.

The most popular explanation of the TDP could be that for the CPUs belonging to the same series, the higher the TDP rating, the better will be the performance. However, it can also be considered as a power wall.

This is because when the set value of the power consumption is reached by the CPU and it is detected by the motherboard, it will down-clock to make sure that the overall stability of the system is maintained.

Ideally, the TDP value of the CPU is affected if it does not support overclocking.

If the TDP is higher, it will offer better performance but at the same time it will also mean higher power consumption and higher temperatures.

On the other hand, if the TDP is marked low, the power consumption by the CPU will be lower, the heat generated will be lower and the power saving will be more.

The relationship between power consumption and TDP of a CPU is complex also due to the reason that people cannot differentiate between energy consumption.

While the formula and parameters of calculating power consumption are mentioned above, that for calculating energy consumption is: E = P*(t/1000).

Here E is the energy in Joules or kilowatt-hours, P is the power in watts, and t is time for which the energy was consumed.

Typically, power consumption can be of two types such as:

  • Dynamic, which is also called as switching power sometimes and
  • Static, which is also called leakage power sometimes.

These can be different but the TDP is considered as the basic indicator for any type of power consumption.

But, as said earlier, this can be lowered by the OEMs sometimes for specific reasons such as:

  • To boost speed and
  • To enhance battery life.

There are different standards to set the TDP of a CPU. For example, Intel has three different standards set for TDP such as:

  • Lower setting, which indicates lower power consumption, lower performance and lower heat and are common in notebooks. This allows controlling power consumption and heat but it may also cause down-clocking and lead to poor performance.
  • Conventional settings, which indicate control of heat and energy consumption and stable performance. This is common in home desktop processors.
  • High settings, which guarantee stability and performance. This is common in server and workstation CPUs.
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Generally speaking, Thermal Design Power now is nothing more than just a measure of the performance of heat of a CPU.

Therefore, you should be unwise to use it as a measure for the power consumption of the CPU.

Therefore, when you choose a power supply for your computer, you should always remember to check that the power rating is not too low in general.

However, for more advanced processes the TDP value can be small because the heat generated will also be small in such cases.

For a 14 nm CPU, the current TDP value is usually 65 watts but when the next generation 10 nm technology will be used, the TDP value will surely become lower, whether it is with or without the K.

Therefore, to sum up, you are true when you say that the actual heat produced by a CPU is not the same as the power consumed by it.

In that case, the CPU will not be of great worth.

In general terms, TDP means the amount of heat that the cooling system that you are using should be able to dissipate in order to prevent it from malfunctioning, failing or melting under utmost perceived load.

This means that a CPU with 100 watt TDP does not mean that it is using 100 watts of power.

It actually means that irrespective of the amount of power being used by the CPU, it needs a maximum of 100 watts of heat to be dissipated in order to operate smoothly at a higher performance level.

Since the CPU does not do any physical work, all electrical power consumed by it is typically given off as heat in one way or the other.

Based on this concept, the TDP is set, which will be hardly reached by the CPU provided it does not have the most horrible piece of silicon allocated to that bin.

And, generally speaking, TDP can never represent the actual power consumption because it primarily tells about the maximum heat value of the processor.

Conclusion

So, coming to the end of this article now you know the difference between the Thermal Design Power of a processor and its power consumption values.

You will not mix up the two anymore like others usually do since you also know which is more important in a processor.

About Dominic Cooper

Dominic CooperDominic Cooper, a TTU graduate is a computer hardware expert. His only passion is to find out the nitty gritty of all computers. He loves to cook when he is not busy with writing, computer testing and research. He is not very fond of social media. Follow Him at Linkedin