i7 4790k temp difference between cores.

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Dawei87

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I just got an i7 4790k and I have a corsair h110 cooler with four fans setup for push/pull. When my cpu is under load whether it is from gaming or even prime95 for 20 minutes my first core and fourth core will vary by 10-12C. My idle temps for my cores are as follows, 31C, 30C, 31C, 25C. And under load (prime95) they are 91C, 93C, 89C, 82C. When gaming or doing real world task I have never seen the temps go above 60C but the fourth core is always much cooler than the others. Is this normal? My i5 4670k in the same pc never ran with more than a few degrees difference between cores.
 
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An i7 4790K runs at a 4.0GHz base clock, where the i5 4670K runs at a 3.4GHz base clock, and also has Hyperthreading , all of which increases core voltage, power dissipation and operating temperatures. If you're overclocked, you haven't mentioned what that clock speed is.

You said your i5 4670K never got above 50C "under load" ... what load? Unless you ran P95 version 26.6 Small FFT's at the same ambient, clock speed and core voltage on both processors, then you have no way to compare apples to apples.

Also, your ambient is about 25C. That's about 3C above Standard Ambient, which is 22C. Intel's thermal Specifications are based on Standard Ambient 22C. Further, at 25C ambient, 70C with Small FFT's is not hot. If we subtract the 3C you...

neon neophyte

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This is completely normal. Let me show you why.

On the die, the cpu and igpu is basically set up like this

[igpu][core1][core2][core3][core4]

As you can see, the only cpu core that isnt sandwhiched inbetween something else which generates heat, is core 4.
 

CompuTronix

Intel Master
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Dawei87,

Intel's Specification for Digital Thermal Sensor (DTS) accuracy is +/- 5C. This means there may be 10C between the highest and lowest Cores, so your processor is a little out of spec.

Other variables include Intel's new polymer thermal compound between the Die and the heat spreader, as well as the thermal compound between the heat spreader and the heat sinc, and how evenly the heat sinc applies pressure to the heat spreader.

When running a thermal test, do not use any version of Prime95 later than 26.6. Here's why:

Core i 2nd, 3rd and 4th Generation CPU's have AVX (Advanced Vector Extension) instruction sets. Recent versions of Prime95 (28.5) run AVX code on the Floating Point Unit (FPU) math coprocessor, which produces unrealistically high temperatures. The FPU test in the software utility AIDA64 shows the same results.

Prime95 v26.6 produces temperatures on 3rd and 4th Generation processors more consistent with 2nd Generation, which also have AVX instructions, but do not suffer from thermal extremes due to having a soldered Integrated Heat Spreader and a 35% larger Die.

Please download Prime95 version 26.6 - http://windows-downloads-center.blogspot.com/2011/04/prime95-266.htm

Please run only Small FFT’s for 10 minutes.

Your Core temperatures will test 10 to 20C lower.

Please read this Tom’s Sticky: Intel Temperature Guide - http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html

Also, what is your ambient temperature?

CT :sol:
 

Dawei87

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Thanks for the quick response! It's good to hear that the temperature difference is normal. I just wasn't expecting it to be anywhere near that much and it had me a little worried.
 

Dawei87

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Thanks for that info! I will try another test with the recommended version of prime95. The ambient temperature in my home is probably about 74-76F. I think that would equal roughly 24C?
 

Dawei87

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After running the Small FFT test with prime95 26.6 I am getting max temps of 70C, 70C, 65C, 58C. Is this still normal? Should this cpu be running this hot with my current cooler? My i5 4670k never got above 50C under load with the same cooler, and I was expecting this cpu to perform roughly the same. Am I being unrealistic in that regard?
 

CompuTronix

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An i7 4790K runs at a 4.0GHz base clock, where the i5 4670K runs at a 3.4GHz base clock, and also has Hyperthreading , all of which increases core voltage, power dissipation and operating temperatures. If you're overclocked, you haven't mentioned what that clock speed is.

You said your i5 4670K never got above 50C "under load" ... what load? Unless you ran P95 version 26.6 Small FFT's at the same ambient, clock speed and core voltage on both processors, then you have no way to compare apples to apples.

Also, your ambient is about 25C. That's about 3C above Standard Ambient, which is 22C. Intel's thermal Specifications are based on Standard Ambient 22C. Further, at 25C ambient, 70C with Small FFT's is not hot. If we subtract the 3C you are above ambient to correct your Core temperatures to Intel's standards, then your results look even better at 67, 67, 62, 55.

Intel's Thermal Specification for your i7 4790K (Tcase) is 74C, which is CPU temperature, not Core temperature. Core temperature is 5C higher than CPU temperature due to sensor location. The corresponding Core temperature is 79C. That's the spec.

Regardless, you still have a consistent 12C spread. It appears that your particular 4790K sample has a DTS sensor that's a little out of spec on the 4th core, as neon neophyte has pointed out. Although a 12C spread isn't quite normal, it's not a problem as long as it's less than the other Cores.

77F = 25C. Here's the temperature conversions and a short scale:

Cx9/5+32=F ... or ... F-32/9x5=C ... or more simply ... an increase of 1C = an increase of 1.8F

30.0C = 86.0F Hot
29.0C = 84.2F
28.0C = 82.4F
27.0C = 80.6F
26.0C = 78.8F Warm
25.0C = 77.0F
24.0C = 75.2F
23.0C = 73.4F
22.0C = 71.6F Standard ... or ... 22.2C = 72.0F
21.0C = 69.8F
20.0C = 68.0F Cool
 
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Dawei87

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Thanks again for the help. Both of my CPU have always been at stock settings and running with turbo mode on. Under the same circumstances my i5 4670k runs much cooler than the i7 4790k. Although I was expecting the i7 to run hotter because it is clocked faster I was not expecting this big of a difference. Especially since the devils canyon CPUs are supposed to have better TIM and run cooler. After more stress testing with the i7 and days of googling and looking at other users temps of the same CPU I have decided that the temp difference I am seeing between cores is not normal and I am going to RMA this chip for a replacement.
 

CompuTronix

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I understand. As I mentioned, Intel's Specifications for Digital Thermal Sensor (DTS) accuracy is +/- 5C. This means there may be 10C between the highest and lowest Cores, so your processor is out of spec.

Please feel free to refer to this thread if it will help with your RMA. Let's just hope that the replacement is in spec. Keep in mind that every processor will have some deviation between cores. Good luck with your RMA.

CT :sol:
 

Dawei87

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Thanks! I do hope the RMA goes smoothly and I get a better CPU. It will probably take at least a week for me to get the replacement in, and if I can remember to do it I might post the results and new temps here just in case that info helps someone else.
 

Dawei87

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OK. So I got the replacement cpu in today and finally got to stress testing it. The temperatures are much more in line with what I was expecting from this cpu. At completely stock settings the chip idles at 28,29,29,31. Under load using prime95 the max temps are 67,72,72,65. My ambient temps might be slightly higher than my previous test with the chip I RMA'd, but I was mostly concerned with the temp difference. I have also noticed that this cpu seems to be getting more power than the old one. My motherboard was sending the old cpu 1.216 volts and this one seems to be getting 1.248 and under load it will actually reach 1.264. So I might try undervolting this chip at some point to bring the temps down. As far as I know this chip should not need more than 1.2 V to run at stock settings with turbo on.
 

Dawei87

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For what it is worth I have been experimenting with undervolting the chip and these are the results:
at 1.2V: 63,65,65,61
at 1.15V: 58,62,60,57

The temps are much better now and everything appears to be stable when running prime95 for more than 10 minutes. Is there anything I should look out for when undervolting? Are there any warning signs I'm not sending the chip enough power?
 

CompuTronix

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rderubeis,

Please be advised that Tom's Moderator Team discourages "Necro-posting", which means posting on a Thread which is 6 months old or more. The reason for this is because of the rapid rate at which computer technology advances, so answers given in older Threads may not apply to current technologies.

Be sure to look at the date on a Thread before posting. Thread is nearly 18 months old. If you have a question, then please start your own Thread.

This Thread is now closed.

CompuTronix :sol:
 
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