TDP

[9enesis]

hallo folks. i am new to this forum . i joined just to add some(probably useful) info.
while reading these type of forums , i came across floating confusion about TDP of CPUs/APUs/GPUs.
i'd like to add here for those who do not feel clear about what TDP is.

first: CPU/APU/GPU is nothing more than an electrical "heater" with a "side effect" of information processing(we exploit as useful work) - that means that (almost) 100% of the electrical energy put in, turns into heat(being lost).

second: thermal design power(TDP).There are(mostly) three types of TDP figuring around: idle,average and maximum.
idle TDP describes the power consumed/dissipated as heat by(CPU/APU/GPU) doing no useful work(just heating up the planet).
average TDP is not worth discussion , because it is vastly load dependent. It could be anywhere between idle and max values.

third: Maximum TDP. It is a value that is used by (CPU/APU/GPU) manufacturers(be it AMD,Intel,Nvidia or whoever else) to provide chip's max requirements of power delivery and cooling.
now what that mean is : whoever decides to use the chip , should be aware that : at stock parameters (like voltage and clocks) , the selected chip might(at some point) consume electrical power which is equal to specified TDP value (for why - see first point) AND then turn it into heat.
This means that: the chip user should be able to provide the max necessary electrical power to the chip first , and then be able to remove it in a form of heat, by using proper cooling solution , for the chip to function properly.

OC = exceeding max TDP provided by manufacturer btw :biggrin:

best regards.

edited.

 

[BrightCandle]

TDP as listed by Intel is not the maximum thermal output. Its actually the expected average peak output under sustained usage, but actually a CPU can consume more than that. For example in the Ivy Bridge mechanical and electrical spec (http://www.intel.co.uk/content/www/uk/en/processors/core/3rd-gen-core-lga1155-socket-guide.html) you will see on page 41 and 42 that a 77W TDP Ivy Bridge will actually at peak pull 95W.

The same is true of graphics cards as well. Furmark was a big thermal push for the cards because it managed to achieve massively higher utilisation than a game could and subsequently push the current usage well above the TDP.

Simply put TDP is no longer measured in the absolute maximum, its more like a guideline for the sustained amount of thermal output over an amount of time but electrically the power system is designed to provide more power than TDP.

 

[boxleitnerb]

Ivy Bridge TDP was set at 95W due to the cooler. They have coolers for 95W and 65W. 65W is obviously not enough and they understandably didn't want to make a new cooler and validate it for 77W, because that is unnecessary and costs money.

 

[9enesis]

TDP as listed by Intel is not the maximum thermal output. Its actually the expected average peak output under sustained usage, but actually a CPU can consume more than that. For example in the Ivy Bridge mechanical and electrical spec (http://www.intel.co.uk/content/www/uk/en/processors/core/3rd-gen-core-lga1155-socket-guide.html) you will see on page 41 and 42 that a 77W TDP Ivy Bridge will actually at peak pull 95W.

The same is true of graphics cards as well. .

No.I think that you are misreading that pdf. the fact that the graph goes higher than 77W for IB cpus , means nothing.
it is all about specification by manufacturer for stock cpu, which is 77W max(in this case). ofcourse you might have some(relatively safe) headroom - that being shown in that graph, but that is about it.

ETA: the(term) max TDP value is one for all the manufacturers , be them samsung , intel , TI etc. It's standard.

".....Datasheets normally contain the thermal design power (TDP), which is the maximum amount of power the cooling system in a computer is required to dissipate. Both Intel and Advanced Micro Devices (AMD) have defined TDP as the maximum power consumption for thermally significant periods running worst-case non-synthetic workloads. Thus, TDP is not the actual maximum power of the processor...."

http://en.wikipedia.org/wiki/CPU_power_dissipation

 

[BrightCandle]

The Thermal design power is about cooling, while it has a relationship with power draw obviously it does not define the peak usage of the CPU. Intel clearly states in its electrical specifications for power delivery that the power draw of the CPU can be greater than the TDP, to the tune of 95W for moments.

You don't need to have cooling for more than 77W but that does not mean that 77W is the peak power draw of the CPU, because for moments its higher than that.

 

[ShintaiDK]

TDP as listed by Intel is not the maximum thermal output. Its actually the expected average peak output under sustained usage, but actually a CPU can consume more than that. For example in the Ivy Bridge mechanical and electrical spec (http://www.intel.co.uk/content/www/uk/en/processors/core/3rd-gen-core-lga1155-socket-guide.html) you will see on page 41 and 42 that a 77W TDP Ivy Bridge will actually at peak pull 95W.

The same is true of graphics cards as well. Furmark was a big thermal push for the cards because it managed to achieve massively higher utilisation than a game could and subsequently push the current usage well above the TDP.

Simply put TDP is no longer measured in the absolute maximum, its more like a guideline for the sustained amount of thermal output over an amount of time but electrically the power system is designed to provide more power than TDP.

A stock IB will never go beyond 77W. You can however change it in BIOS for a new TDP limit to reach 95W for more turbomodes. And up to 95W is still under warranty.

 

[9enesis]

The Thermal design power is about cooling, while it has a relationship with power draw obviously it does not define the peak usage of the CPU.

it does or to be precise - 2nd law of thermodynamics states that.

Intel clearly states in its electrical specifications for power delivery that the power draw of the CPU can be greater than the TDP, to the tune of 95W for moments.

i'd like to see a direct quote of this,please.

You don't need to have cooling for more than 77W but that does not mean that 77W is the peak power draw of the CPU, because for moments its higher than that.

nope.for example: You cannot design a laptop that way.

edited.

 

[BrightCandle]

The Intel document clearly states (section 6, specifically 6.3.5.1) that the power limit is 1.25 x TDP. The document even has a nice picture showing you what this means in terms of power consumption in that same section. There are notes in the earlier sections that also state it can be higher than TDP and then that section specifies how much higher. The time for which it can exceed it is 28 seconds and then a much larger exceed for 10ms.

I can't do anything but point at your "nope" with zero evidence and chuckle to myself "Just another wrong guy on the internet". I am trying to help you understand and grow not tell you that your wrong. Please read the document.

 

[9enesis]

The Intel document clearly states (section 6, specifically 6.3.5.1) that the power limit is 1.25 x TDP. The document even has a nice picture showing you what this means in terms of power consumption in that same section. There are notes in the earlier sections that also state it can be higher than TDP and then that section specifies how much higher. The time for which it can exceed it is 28 seconds and then a much larger exceed for 10ms.

I can't do anything but point at your "nope" with zero evidence and chuckle to myself "Just another wrong guy on the internet". I am trying to help you understand and grow not tell you that your wrong. Please read the document.

the chapter you refer to is not in your favor - it does not state what you said. What it tells is that you CAN customize power package. it is obvious you did not read the document - just grabbed something to throw at me.

 

[know of fence]

BrightCandle is right, he put in the effort to find the document and point out the relevant parts. Another passage stating they aren't the same thing.

Analysis indicates that real applications are unlikely to cause the processor to consume
maximum power dissipation for sustained time periods. Intel recommends that
complete thermal solution designs target the Thermal Design Power (TDP), instead of
the maximum processor power consumption. The Adaptive Thermal Monitor feature is
intended to help protect the processor in the event that an application exceeds the TDP
recommendation for a sustained time period. (6.1 Thermal Specs, p.39)

But that doesn't mean it always has been that way... but TDP always was measureed as heat according to this source, presumably meaning [Joule / s = W] rather than just [V*A = W] http://www.lostcircuits.com/mambo//...task=view&id=44&Itemid=1&limit=1&limitstart=0
With the TDP chip makers are in a lose-lose situation, low TDP would suggest low OC headroom high TDP means loud, hungry and eco-unfriendly, so they are trying to disassociate it from both of those things. I wouldn't be surprised if we got something like cooler rating A to F instead of TDP for graphics and cpu in the near future, with sites like AT recommending the Corsair Double D power supplies.

 

[ShintaiDK]

The CPUs draw more power for a fraction when moving between states. But overall in the timeline its nothing more than a blink.

Under 100% peak heavy load the CPUs will not go beyond their TDP at 77W substained.

 

[9enesis]

ok now that i re-read that part - indeed i was wrong. the 1,25X times power is indeed the default value. first i was reading it as being a custom enbled feature to exceed power limit and thus max TDP value for short periods of time.

sorry - my bad. but it still doesn't change a thing about max TDP - it is what is stated by intel - 77W(in this case)

 

[9enesis]

TDP always was measureed as heat according to this source, presumably meaning [Joule / s = W] rather than just [V*A = W]

Watt is a Watt it doesn't matter heat watt or electrical watt - either way it is power measurement.

if you like to nitpick you can convert everything into joules - as the result what you will get will be => electrical energy in = heat energy out(almost)

thus what i stated is also correct(roughly though) that max TDP of 77W = electrical 77W in. AS you exceed electrical max power of 77W , you also increase the generation of heat , thus exceeding the max TDP value(77W).

 

[9enesis]

Under 100% peak heavy load the CPUs will not go beyond their TDP at 77W substained.

this