High temps with Matterhorn Pure on 4790K 4.4GHZ 1.178V

istenEM,

Your cooler is a bit uncommon, so I checked the specs and reviews, which reveal that it's a decent mid-range cooler. 87C is high, so a few questions:

What is your ambient temperature?

Which version of Prime95 did you run?

CT

I wouldn't get stuck on LinX Core temperature results. Here's the thing:

Test utilities such as LinX, LinPack, Intel Burn Test and versions of Prime95 later than 26.6 load your CPU beyond 100% TDP at default BIOS settings. Intel tests their processors at 100% TDP with the intended default settings specified for motherboard manufacturers. So when the end user is running thermal and stability tests, the goal is to replicate Intel's test parameters as closely as possible using compatible test methods.

This means that when your 88 Watt TDP i7 4790K is installed with the stock cooler on a motherboard with default settings, then Prime95 v26.6 Small FFT's is run, a utility such as Core Temp or HWMonitor should show that Power (Watts) is within 3% of TDP, which is approximately 85 to 91 Watts. Of course, the values change when we modify BIOS settings and install after-market coolers to overclock our processors, but this shows that our test methods are appropriate.

Prime95 version 26.6 Small FFT's meets Intel's TDP specification more closely than any other utility. Also, Small FFT's is a steady workload which is perfect for evaluating thermal performance and Core temperatures. Just take a look at Section 13 in the Temperature Guide. You can see that the Charts show what a steady workload looks like compared to fluctuating workloads.

Asus RealBench is excellent for stability testing. Although it runs a fluctuating workload, it also runs your CPU within 3% TDP during peak workloads, but it uses a realistic AVX workload with code from HandBrake, yet provides peak Core temperatures consistent with Prime95 V26.6 Small FFT's.

The problem with this topic is that there's so much confusion concerning Intel's specifications, and thus so much misinformation out here, and so many people using so many different haphazard approaches to testing without any solid basis or understanding, that it's nearly impossible to compare apples to apples. This is why I wrote the Intel Temperature Guide. Give it a read.

CT

Vcore affects stability much more than any other parameter. A bump of just 10, 20 or 30 millivolts is not enough for another 100 MHz; you need 50 millivolts (0.050). And changing the Cache multiplier from 40x to 42x will only destabilize your processor.

Here's what's in the Temp Guide in Section 9 - Overclocking and Voltage

Overclocking is always limited by two factors; voltage and temperature. As Core speed (MHz) is increased above a level unique to each processor (silicon lottery), Core voltage (Vcore) must also be increased to maintain stability. This increases power consumption (Watts) which results in increased Core temperatures.

Overclocked processors using increased Vcore can run up to 50% above TDP. This is why high TDP air or liquid cooling is critical to keep Core temperatures under 80C. Overclocking should not be attempted with Vcore settings in “Auto” because BIOS will apply significantly more voltage than is necessary to maintain stability.

Even when using manual Vcore settings, excessive Vcore and temperatures may result in accelerated "Electromigration" - https://www.google.com/?gws_rd=ssl#q=Electromigration

This prematurely erodes the traces and junctions within the processor's layers and nano-circuits, which will eventually result in blue-screen crashes that become increasingly frequent over time. CPU's become more susceptible to Electromigration with each Die-shrink. However, Intel's advances in FinFET technology has improved the voltage tolerance of their 14 nanometer architecture.

Here’s a list of the maximum recommended Vcore settings:

-> Core i

6th Generation 14 nanometer ... 1.375 Vcore
5th Generation 14 nanometer ... 1.375 Vcore
4th Generation 22 nanometer ... 1.300 Vcore
3rd Generation 22 nanometer ... 1.300 Vcore
2nd Generation 32 nanometer ... 1.350 Vcore
Previous Generation 32 nanometer ... 1.350 Vcore
Previous Generation 45 nanometer ... 1.400 Vcore

-> Core 2

Legacy 45 nanometer ... 1.400 Vcore
Legacy 65 nanometer ... 1.500 Vcore

When tweaking your processor near it's highest overclock, keep in mind that for an increase of 100 MHz, a corresponding increase of about 50 millivolts (0.050) is needed to maintain stability. If 75 to 100 millivolts or more is needed for the next stable 100 MHz increase, it means your processor is overclocked beyond it's capability.

With high TDP air or liquid cooling you might reach the Vcore limit before 80C. With low-end cooling you’ll reach 80C before the Vcore limit. Regardless, whichever limit you reach first is where you should stop and declare victory. Testing is explained in Sections 11 through 14.

Remember to keep overclocking in perspective. For example, the difference between 4.4 GHz and 4.5 Ghz is less than 2.3%, which has no noticeable impact on overall system performance. It simply isn’t worth pushing your processor beyond recommended Core voltage and Core temperature limits just to squeeze out another 100 MHz.

CT

Your Vcore is fine and your Core temperatures are still OK, but remember that all computer temperatures rise and fall with ambient temperature. Leave yourself enough thermal headroom for warmer ambient temperatures during the summer season.

Try this: http://rog.asus.com/articles/news/realbench-v2-43-new-version-available-now/

Click on the word "download" shown in bold print.