What's a normal temp delta between cooler and CPU under stress (8086K/H150i)?

I've got a 150i in a 500D RGB case, 9 fans, push-pull on the radiator. Everything (fans + pump) set to quiet. 8086K running at its stock multiplier and voltage, no gpu at the moment. Asus Maximus X Hero (AC Wifi). CPU generally idles in the high 20s-low 30s, ambient temp around 22-23C.

When I run Prime95 the CPU works its way up to the low-mid 70s while the H150i Pump temp works it way up to around 36C during the same time. I would have expected the coolant temperature to rise higher - a 35-40C delta between CPU temp and cooler temp seems rather large to me..? H150i pump speed stays at around 1100-1150. Fans linked to coolant rev up to about 650rpm once coolant temp hits 35C (using quiet profile, no custom profiles). 32gb Vengeance Pro RGB 3600mhz DDR4 ram hits low 50s during Prime95 (running its XMP profile).

Does this suggest either a poor interface between the CPU and its lid/lid and cooler - or is this sort of temperature difference normal under stress?

Any guidance much appreciated - thanks!

I am afraid a 35C+ differential between coolant and core temps is about the absolute minimum for a non-delid CPU in the 6700-8700K series. That value is all about voltage and the CPU materials. Plenty of criticism out there regarding Intel's TIM construction on recent models and the 8086 has a lot of clock speed right out of the box. You didn't mention your actual Vcore during the test (not what is set in the BIOS). Asus sets you up to run hot on their Z370s with Multi-core enhancement (MCE) and some heavy handed load line settings. Prime may exacerbate the results further, depending on how you configure the run. If your delta was only 35-40C, it was not out of control. I see stock set-ups at +50C when run on the initial defaults.

For comparison, my 8700K at 5.0/1.30v will run a coolant delta of about +6C during a full blast CPU stress test. Most of the time less. However, mine is delidded at thus the coolant to core differential is much lower. I see +30-35 in worst case scenarios at 1.30v.

The one suggestion I would make (aside from a few BIOS tweaks depending on how you want to run) is to set the pump to Balanced. That should be about 2100 rpm. In most testing I have done on the H115i PRO and others on the H150i, there is some reduction in performance at the Quiet/1100 rpm speed. If you want to use that around the desktop, go right ahead and it makes no difference. It probably will cost you 2-3C in coolant/CPU temp during heavy load. Since the pump is fixed and there are no dynamic adjustments, I usually recommend most people set it to Balanced and leave it. On the other end, no one is reporting gains by using the extreme 3000 rpm setting, so I don't see a reason to use it. Unlike the balanced, it is much easier to hear at idle. We are talking about a few degrees either way and these last several generations of Intel CPU are all voltage and materials limited. We all have too much cooler, but the nice thing is you can let those 3x120 fans just trickle along and the still get efficient cooling.

I am afraid a 35C+ differential between coolant and core temps is about the absolute minimum for a non-delid CPU in the 6700-8700K series. That value is all about voltage and the CPU materials. Plenty of criticism out there regarding Intel's TIM construction on recent models and the 8086 has a lot of clock speed right out of the box. You didn't mention your actual Vcore during the test (not what is set in the BIOS). Asus sets you up to run hot on their Z370s with Multi-core enhancement (MCE) and some heavy handed load line settings. Prime may exacerbate the results further, depending on how you configure the run. If your delta was only 35-40C, it was not out of control. I see stock set-ups at +50C when run on the initial defaults.

 

For comparison, my 8700K at 5.0/1.30v will run a coolant delta of about +6C during a full blast CPU stress test. Most of the time less. However, mine is delidded at thus the coolant to core differential is much lower. I see +30-35 in worst case scenarios at 1.30v.

 

The one suggestion I would make (aside from a few BIOS tweaks depending on how you want to run) is to set the pump to Balanced. That should be about 2100 rpm. In most testing I have done on the H115i PRO and others on the H150i, there is some reduction in performance at the Quiet/1100 rpm speed. If you want to use that around the desktop, go right ahead and it makes no difference. It probably will cost you 2-3C in coolant/CPU temp during heavy load. Since the pump is fixed and there are no dynamic adjustments, I usually recommend most people set it to Balanced and leave it. On the other end, no one is reporting gains by using the extreme 3000 rpm setting, so I don't see a reason to use it. Unlike the balanced, it is much easier to hear at idle. We are talking about a few degrees either way and these last several generations of Intel CPU are all voltage and materials limited. We all have too much cooler, but the nice thing is you can let those 3x120 fans just trickle along and the still get efficient cooling.

Thanks so much c-attack, this is very helpful. I will set the pump to Balanced.

I am surprised that the delta at stock setting is normally in that 35C area, makes it very tempting to delid this fella and apply some Kyronaut at the very least.

As for stock CPU voltage, I'm not 100% sure how to measure this outside of the bios setting (zero offset), but the reading from the Maximus motherboard vcpu is at 1.20v according to iCUE. Note, I do have MCE enabled in the BIOS.

Given voltage at least appears to be hovering around 1.20v, are you still content that this ~35C delta is normal?

Thanks again mate, I sincerely appreciate the guidance.

PS: I notice you have a Seasonic 1000W Prime - I'm also using a Seasonic 1000W Prime Ultra Titanium - I notice that, when it's not in Hybrid mode, its fan makes a "brrrr" noise which is audible from over a meter away and through a wooden desk-top. Is this normal? My corsair fans (even the LL120s) are super quiet even up to about 700 rpm...? Was thinking about swapping the Seasonic for a Corsair 1000W HXi

1.20v peak with MCE on is not bad. Perhaps Asus has softened the edges on some these recent BIOS versions. 6 months ago it was common to see 1.40v with MCE on and running a stress test. You have an additional tool to shape that VID curve. At the top of the Extreme Tweaker column in the BIOS is a 'CPU SVID Behavior' setting. It toggles between Worst Case, Normal, Best Case, and AUTO. Essentially, this is a whole curve offset for Auto/Adaptive voltage. It used to be AUTO assumed worst case, which is where things went wrong. Perhaps that was the tweak. Either way, setting it to best Best Case will keep the voltage piling on to a much trimmer level when using Auto or Adaptive. Either way, I think +35C is about the minimum for unmodified settings, so I do not see a contact issue. My 8700K is delided so, I can't make a straight comparison. My coolant/core differential was about +20C at default settings, so that does seem right.

The other thing to do if using Auto/Adaptive is go into the CPU Power Management sub-menu from the Extreme/AI Tweaker column. At the bottom of this sub-section are the Load Line IA and DC settings. Set both to 0.01. That should prevent unnecessary voltage pile on under load conditions. It is better shown here in the Asus Z270 OC guide. (3rd slide from the top).

I get a very brief "whirrrrrr" when the fan powers on (I leave it in the Eco mode/passive state). It apparently must go full 12v on the start-up before settling down to its normal slower speed. I have mixed feelings. I remember reading all the user reviews about the "wonderfully quiet fan". No. It sounds like a blender at very slow speed. The bright side is that level of noise is inaudible when at load and the rest of the system is churning and/or headphones on. I still hear the whirr power on through the headphones, but it is very infrequent and this Titanium model really is efficient. Even in the worst of summer in a 30C room, it does not kick on very much and never at lower loads and yesterday when I was pulling 550W out 1000W for a few hours, it still behaved. For my use, it works without much irritation. The irony is I only bought it to replace a EVGA supernova 1200W that was otherwise fine, except disabling its ECO mode made the fan run at 100%, all the time. In Summer not running the fan would heat up the SSDs parked above it by about 10C and I couldn't quite get to the fan on trigger very often. On both, the PSU fan is the most obnoxious moving device in the system. Ugh.. I see what you mean. I turned it on manually while writing this. It's terrible. Not even a loud, but smooth ball bearing noise. Rickety and sharp. Yeah, I probably would have gone with a Corsair PSU, but their current offerings did not meet my requirements. I was really hoping they would come out with a revamp of their current AXi line up. Didn't happen.

Following up, I delidded and relidded my 8086k last night/this morning. Temps running Prime95 (v.29.4, small FFTs) have gone from mid-high 90s before down to low-mid 70s now. Wowsers.

This was using LM (Conductonaut) on the CPU die/IHS underside. I used Kryonaut paste between the top of the IHS and the h150i cooler block. Very happy with the result. Desktop stays whisper quiet even when running P95.