Why are the max CPU base clock speeds are 4.0 ghz?

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TheFinalEpic

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Nov 6, 2015
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This always bugged me. I'm mostly a gamer and i sometimes render videos but thats it. Games greatly enjoy high single threaded performance, with future games scaling with quad cores and not much more than that.


I know not all GHZ are not made equal but the highest clock speeds have always been 4.0, with 2600k, 4790k, 6700k, etc. and they're always quad cores. (I know 6700k is only a tiny bit faster than i7 4790k and a tad fastrer than 2600k).


So my questions are:

Why cant quad cores or any cpu for that matter, have a higher stock clock speed than 4.0ghz?

Also why does 6 cores, 8 cores, 10 cores etc, never reach higher than the 3.0-3.5 ghz range? Why can't they have 4.0 ghz also?
 
Solution
Ecky
Clockspeed is partly determined by architecture. A longer pipeline generally allows for higher clocks, but reduced performance per clock.

Power consumption goes up exponentially with clockspeed, so it's often in a manufacturer's best interest to keep clocks low and increase performance per clock. For instance, an FX-8320E turbos to 4ghz with a 95w TDP, FX-8370 turbos to 4.3ghz within a 125w TDP, and FX-9590 turbos to 5ghz with a 220w TDP. TDP isn't power consumption, but it's often close, and going by that the 8370 delivers 7.5% increased performance for 32% more power consumption, and the 9590 delivers 25% more performance for 132% more power consumption.
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The_Man12

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Mar 22, 2014
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The stock clock speed is usually decided by the manufacturer, usually Intel. I've seen that usually 4Ghz is the sweet spot for quad cores with air cooling.

Usually CPUs with more than 4 cores don't have a base clock speed that high because more cores = more heat and power consumption. If I was to run a quad core CPU at 4Ghz and a 10 core CPU at 4Ghz, the 10 core CPU would generate more heat and need better cooling to stay cool.

So remember!

More cores = More heat and power consumption
 
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scuzzycard

scuzzycard

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Feb 26, 2016
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Another factor besides thermal issues is that Intel has a target TDP (thermal design power) that they are trying to hit. Higher wattages mean not only more heat, but motherboards and Power Supplies to cope with that current draw. Finally, there is pressure on corporations to produce products that conserve energy. It wouldn't surprise me if Intel didn't have to meet certain goals to qualify for certain tax breaks.

For example a 5960X's stock (non-turbo) setting is 3.0GHz at 0.95V, when it has the same basic architecture as a 4790K that is 4.0GHz at 1.15V. In this way, the 5960X is able to have a rating of 140W, even though it has twice as many cores as a 4790K (88W).
 
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viewtyjoe

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Jul 28, 2014
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The biggest reasons are dispersed power (TDP) and cooling. Before the advent of consumer multi-core CPUs, AMD and Intel were basically in a race to push architectures faster and faster, and they both found that around 4GHz the gains in CPU performance stop being worth the losses (extra heat/power). Obviously, with some luck and adequate cooling, processors can be pushed beyond 4GHz, but for something that is meant to run all day for non-technical users, 4Ghz is more or less the top end of what's viable.
 
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Ecky

Ecky

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Feb 3, 2013
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Clockspeed is partly determined by architecture. A longer pipeline generally allows for higher clocks, but reduced performance per clock.

Power consumption goes up exponentially with clockspeed, so it's often in a manufacturer's best interest to keep clocks low and increase performance per clock. For instance, an FX-8320E turbos to 4ghz with a 95w TDP, FX-8370 turbos to 4.3ghz within a 125w TDP, and FX-9590 turbos to 5ghz with a 220w TDP. TDP isn't power consumption, but it's often close, and going by that the 8370 delivers 7.5% increased performance for 32% more power consumption, and the 9590 delivers 25% more performance for 132% more power consumption.
 
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Solution
gamerk316

gamerk316

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Jul 8, 2008
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Short Answer: Physics

Basically, a higher clock leads to more power draw, and as a result, more heat. And the curve is exponential; you need exponentially more cooling as power draw increases, making it not cost effective to increase clocks much beyond 4Ghz.
 
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scuzzycard

scuzzycard

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Absolutely - I enjoyed checking up on this thread - everyone tackled the question from a completely different perspective.
 
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