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 Post subject: Why Intel Processors Draw More Power Than Expected
PostPosted: Fri Nov 09, 2018 8:13 pm 
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Interesting article on Anandtech:

Quote:
Why Intel Processors Draw More Power Than Expected: TDP and Turbo Explained

One of the recent topics permeating through the custom PC space recently has been about power draw. Intel’s latest eight-core processors are still rated at a TDP of 95W, and yet users are seeing power consumption north of 150-180W, which doesn’t make much sense. In this guide, we want to give you a proper understanding why this is the case, and why it gives us reviewers such a headache.
What is TDP (Thermal Design Power)?

With every processor, Intel guarantees a specific frequency at a specific power, often with a particular grade of cooler in mind. Most people equate a chip's TDP rating directly to its maximum power draw, given that the heat energy that needs to be dissipated from the processor is equal to the power consumed in doing calculations. Normally, the TDP rating is that specific power.

But TDP, in its strictest sense, relates to the ability of the cooler to dissipate heat. TDP is the minimum capacity of the CPU cooler required to get that guaranteed level of performance. Some energy dissipation also occurs through the socket and motherboard, which means that technically the cooler rating can be lower than the TDP, but in most circles TDP and power consumption are used to mean the same thing: how much power a CPU draws under load.


More:
https://www.anandtech.com/show/13544/wh ... -tdp-turbo


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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Sat Nov 10, 2018 11:36 am 
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Edited to add quote punctuation.

Yeah, a bunch of sites have chimed in on this.

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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Mon Nov 12, 2018 12:00 am 
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Yes, it's an interesting topic.
Quote:
... in most circles TDP and power consumption are used to mean the same thing: how much power a CPU draws under load.
Just to be clear, it should read:
"... how much power a CPU draws in average, over a time span, while under a typical load."
It's never been the peak power draw at some torture test.

Anyway, AMD's Wraith Spire cooler is rated for 95W and known to allow some overclocking with AMD's "95W" Ryzen CPUs.
I wonder how much you can overclock a Core i9-9900K using that cooler?


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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Thu Jan 24, 2019 3:55 am 
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Olle P wrote:
I wonder how much you can overclock a Core i9-9900K using that cooler?


My brother got an i9-9900K with a NH-U14S last week. On worst case P95, without any overclocking it goes north of 200W (according to HWMonitor) and flirts with 90C (Noctua at its 1500rpm max). Real world work load is considerably lower, but still, crazy!


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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Thu Jan 24, 2019 8:21 am 
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Intel's watt ratings are thermal watts (TDP = Thermal Design Power) not electrical watts. They are supposed to be a guideline for OEMs about how much cooling a CPU is likely to need. And incidentally the ratings are calculated at stock clocks, so they don't take account of turbo modes. So Intel Processors don't draw more power than expected, people are just confusing what type of watt they are dealing with.

I don't think the TDP ratings are particularly useful in real world use. How hot a CPU runs depends on a number of factors, for example ambient temperature and how much airflow you have through a case. Running with fewer case fans or running case fans at lower speeds will potentially push CPU temps higher. Using PWM fans or 3-pin fans that are configured to speed up as the CPU gets hotter can limit maximum CPU temperatures. Fixed fan speeds, particularly fixed lower fan speeds in the interests of quietness, can lead to CPU temps escalating rapidly. If you are not worried about noise levels, CPU cooling under load is not likely to be an issue. If the aim is to have a quiet or quieter PC it becomes more difficult.


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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Fri Jan 25, 2019 2:29 am 
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Average thermal W = average electrical W.


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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Fri Jan 25, 2019 3:22 am 
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No, absolutely not. To take a real world example, the thermal power of a nuclear power plant is usually about three times its electrical power.


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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Sat Jan 26, 2019 7:02 am 
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lodestar wrote:
No, absolutely not. To take a real world example, the thermal power of a nuclear power plant is usually about three times its electrical power.

Your comparison is irrelevant and incorrect. A power plant converts thermal energy into electricity. Any kind of electric appliance does not, but does the inverse.

However, any kind of electric appliance does something (the usefull stuff) and the rest is converted into heat. When talking about processors, Klusu is correct. All of the power it uses is converted into heat (there is no other useful payload here, into which a significant amount of the W is converted into).

There are other components which also produce heat, like the MB, power supply etc (and the efficiency of these is far below 100%). These need to be taken into account. If wattage is measured from the wall, then practically all of that is converted into heat (well, there are things like LEDs, fans etc. so some is converted into light and kinetic energy, but the proportion is very small and is often converted into head eventually, by e.g. friction or photons hitting something).


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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Sun Jan 27, 2019 5:02 am 
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The problem with TDP is that its only real when the CPU and the mothebroard is run with Intel specs on everything.... and there are specs like turbo sustained timing among a lot of other things that keep it in a certain TDP, but most good motherboard violate this, making 95W TPD CPUs like 9900k be a 150W+ TDP, honestly TDP for me its worthless, it should be removed or make it a range, into where you can see the intel speced and the max it could reach, like 95-200, but even then it would hard to predict accurately with many motherboard vendors doing their own bios implementations and tweaks... either way for me its worthless.

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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Thu Feb 14, 2019 6:31 am 
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lodestar wrote:
... And incidentally the ratings are calculated at stock clocks, so they don't take account of turbo modes. So Intel Processors don't draw more power than expected, people are just confusing what type of watt they are dealing with.
I don't think the TDP ratings are particularly useful in real world use.
1. With all cores loaded over a significant time the CPU should run at stock speed. Any more than that will be considered overclocking.
2. Boost speed is for use a) while the CPU is still cool and just getting a task to perform, or b) when less than all cores are utilised so there's power to spare.
3. The TDP is useful when you are about to build thousands of computers (to be sold) and want to keep the production cost down to a minimum. You design the cooling solution based on the TDPs of the parts used.


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 Post subject: Re: Why Intel Processors Draw More Power Than Expected
PostPosted: Fri Mar 01, 2019 1:56 pm 
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Great post. Thanks for the information.


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