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rapid Change in Temp/Time = good thermal conductivity?

If a system is at 100% CPU usage at 60C and drops to 25C within 2 seconds when the system falls to 5% CPU usage, does this indicate good or bad thermal transfer?

 

I've noticed that my de-lidded CPU with liquid ultra under the IHS doesn't get better cooling. It's almost exactly the same as before. That might be on the H80i and it's thermal capacity, but I have noticed what I mentioned above.

 

Thanks in advance for your experience.

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9 minutes ago, Tiberiusisgame said:

does this indicate good or bad thermal transfer?

bad

the heat sink effectively should soak up some of that heat and you'd have a situation where as the cpu is cooling down , the heat sink is effectively warmer than the cpu and makes the drop more gradual. Although if it's a water cooler it very well may be that the cpu isn't heating up the block at all. which means when it's not under load the block is able to rapidly cool the cpu.

The rapid temperature changes shouldn't be a problem at all. just the max temp.

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1 hour ago, Tiberiusisgame said:

If a system is at 100% CPU usage at 60C and drops to 25C within 2 seconds when the system falls to 5% CPU usage, does this indicate good or bad thermal transfer?

 

I've noticed that my de-lidded CPU with liquid ultra under the IHS doesn't get better cooling. It's almost exactly the same as before. That might be on the H80i and it's thermal capacity, but I have noticed what I mentioned above.

 

Thanks in advance for your experience.

Actually it means the oposite. The larger the thermal resistance, the larger the temperature step on a rapid usage change.

On the other hand, 60°C is perfectly fine, and you don't have to worry al all.

Mineral oil and 40 kg aluminium heat sinks are a perfect combination: 73 cores and a Titan X, Twenty Thousand Leagues Under the Oil

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It's pretty funny that as soon as I posted this, Steve comes out with a video on what they've learned with regards to de-lidding. I'm still testing this scenario and researching it. Based on 2 perspectives, I can't definitively say anything.

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On 04/01/2018 at 4:58 AM, Tiberiusisgame said:

If a system is at 100% CPU usage at 60C and drops to 25C within 2 seconds when the system falls to 5% CPU usage, does this indicate good or bad thermal transfer?

 

I've noticed that my de-lidded CPU with liquid ultra under the IHS doesn't get better cooling. It's almost exactly the same as before. That might be on the H80i and it's thermal capacity, but I have noticed what I mentioned above.

 

Thanks in advance for your experience.

The quick drop in temperature does not really indicate anything about the transfer efficiency except for the fact that you haven't saturated your AIO sufficiently.

 

I hope it is fairly clear to all that the fact that the CPU drops instantly to 25 degrees must indicate that the coolant temperature in the AIO is 25 degrees or less, as well as the fact that the ambient room temperature must also be 25 degrees or less.

 

This means that the coolant in the AIO had not sufficiently heated up to equilibrium during stress testing due to the high heat capacity of water/ethylene glycol. If the coolant has indeed heated up to say 40 degrees for example, then you expect the CPU to idle at this temperature for a while before gradually cooling down. To test AIOs you really need to put the load on for tens of minutes to give the coolant a chance to warm up.

 

Since your CPU doesn't cook itself under load, to me indicates that there is at least some thermal transfer between the IHS and the cooler. However the fact the delidding did not improve the temps indicate to me either you have a low heat generating CPU or non overclocked that didnt' kick enough heat in the first place. Another explanation is that indeed you have poor thermal transfer between the IHS and cooler and that is bottlenecking the thermal transfer and so improving the die IHS contact does not help the temps under load. 

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17 hours ago, For Science! said:

...

Extremely useful and very interesting analysis!

 

I can confirm that this was a non-overclocked 4790K (so under 90 Watt draw) de-lidded with liquid metal between die and IHS in a room with an ambient room temperature around 16C (60F) and I only ran the test for 20 minutes.

 

I didn't think to test this configuration with an OC before I de-lidded it, which was clearly a mistake.

 

I used MX-4 between IHS and cooler, same as I've always used.

 

My goal was lower idle temperatures to reduce fan speed.

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On 1/10/2018 at 4:11 PM, Tiberiusisgame said:

My goal was lower idle temperatures to reduce fan speed.

Then I'd suggest changing the fan curve so it's completely silent up until 40-50C. My fans are on the lowest possible speed, until the cpu reaches 45C.
I'm sure you saw with the stock tim how the temp jumped for 30 to 65 in a millisec. That's what shows bad cooling. When it's the other way around, it means that the coolant is still "cold".

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Oh you're absolutely right. In fact, after a cable re-sleeve, I missed connecting one of the fans on the CPU radiator (push pull) and never even noticed. In the winter when my basement is 15C, I barely need fans.

 

Is there a place where data like this is logged? Somewhere on Steve's site? I mean, it applies to so few people, but for those who have experience with it, that's a wealth of knowledge for diagnostic purposes.

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