TDP (short for thermal design power, or thermal design point) is a measurement of how much heat is generated by electronic hardware, such as a CPU. For example, a CPU cooler rated for 65 W TDP can dissipate the heat generated by 65 W (watts) of electricity. TDP rating indicates how much power is required by an individual component of a computer.
TDP ratings may vary depending on hardware manufacturer. Therefore, the TDP listed by one manufacturer may not compare exactly to that of another.
What does TDP indicate?
Within the same generation of processors, those of a higher frequency generally use more power, and have a higher TDP. Other factors affect how much power is used by a CPU, including its number of cores and the size of its onboard memory cache.
However, TDP does not necessarily correlate to performance. Dennard scaling dictates that as circuitry becomes smaller, it becomes more efficient, consuming less power while achieving greater performance. For this reason, processors fabricated with a smaller process node (and therefore smaller transistors) may be more powerful than those with a higher TDP.
A rule of thumb is that a CPU with higher TDP than another is either more powerful, or less efficient, or both.
Why is TDP important?
If you are building your own computer system, two of the most important factors are power and cooling. Your PSU must provide adequate power for all the components in your system, and the heat inside the computer must be adequately removed.
When choosing a PSU, it's a good idea to look up the specifications for all hardware in your system, including motherboard, RAM, CPU, GPU, and disk drives, and add up the TDP of each. This total TDP, measured in watts, represents the amount of power your PSU must provide. Ensure that you install a PSU rated to provide at least that many watts of power, plus about 100 watts, to account for variance in TDP ratings and real-world usage. If you plan to add additional hardware to the computer later, budget for that expected increase in TDP when you choose your PSU.
For each component that requires passive or active cooling, ensure that its cooler is rated to dissipate the same or greater TDP than the component. So, if your CPU has a TDP of 65 watts, make sure its heat sink and fan are rated to dissipate at least that much heat. The same is true if you are using a liquid cooling system.
For comparison, the following is a list of different CPUs, their TDP, frequencies, number of cores, onboard cache, fabrication process, device type, and price.
|CPU||TDP||Freq (base, max)||Cores||L1, L2, L3 cache||fabrication||Device type||Retail price|
|AMD Threadripper 2990WX||250 W||3.0, 4.2 GHz||32||3, 16, 64 MB||12 nm||Servers, workstations||$1799|
|Intel i9-9900K||95 W||3.6, 5.0 GHz||8||512 KB, 2, 16 MB||14 nm||High-end desktop||$499|
|Intel i9-8950 HK||45 W||2.9, 4.6 GHz||6||384 KB, 1.5, 12 MB||14 nm||High-end laptop||$583|
|Qualcomm Kryo 485||5 W||1.8, 2.8 GHz||8||n/a, 512 KB, 5 MB||7 nm||High-end smartphone||n/a|