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 2022-01-05, 02:16 #1 ThomRuley     May 2003 3×97 Posts Liquid cooling I just built a new rig and everything was going fine for the first 2 days or so. Then I looked at task manager and noticed the CPU had throttled back to 75%. After checking the temperature, the CPU was running right at 100C. I'm currently using air cooling primarily with a CoolerMaster fan and a very generous heatsink. This combined with two additional case fans does not appear to be adequate for prime95 on an i9. I was considering upgrading to a liquid cooling system, but had a few questions for someone with more experience in this area: -Do I actually need a liquid cooling system or is there a way to improve the air cooling to get the job done? -If I do install liquid cooling, what are some things I need to know beforehand? -Are there any particularly good models for liquid cooling? Let me know if you need any additional information. I'm also happy to include pictures if that helps (I would like to confirm that my fan is on the correct side of the heatsink).
 2022-01-05, 03:55 #2 Mark Rose     "/X\(‘-‘)/X\" Jan 2013 295210 Posts Are you overclocking? Which i9 specifically? Air cooling is generally more reliable and cheaper if under you're 200 watts. Because of that, I've never been able to justify the expense of water cooling.
 2022-01-05, 04:42 #3 DrobinsonPE   Aug 2020 100010012 Posts I cannot answer your questions directly but can provide you with some food for thought. What are you trying to do with this computer? Are you primarily using it for something where you really need all that power or are you using it primarily to find the next prime number? I have a computer with an i7-9700K CPU and a GTX-1650 Super. It was for a time, the most powerful computer I owned. Sometimes my daughter uses it for a highschool graphics art assignment, sometimes I use it for other things, but right now, most of the time it just runs Prime 95. Unfortunately, like you, I realized early on that it got really hot very quickly and was going to need an expensive cooling system to run at its full potential. Instead of buying a liquid cooler or a very large and expensive air cooler, I decided to try underclocking the CPU first. It turned out that the processor could be underclocked significantly with little to no effect on Prime 95 calculation speed but a significant impact on power use. Here are some select examples from my testing: 4900 MHz = 3.218 ms/ittr = 154 W power use 4000 MHz = 3.219 ms/ittr = 153 W power use 3100 MHz = 3.221 ms/ittr = 102W power use 2300 MHz = 3.298 ms/ittr = 81W power use 1800 MHz = 3.531 ms/ittr = 71W power use One thing to note about the numbers above, the power use is for the entire computer, not just the processor. This computer is currently BIOS limited to 2000 MHz. At that speed it has a 5% reduction in Prime 95 output with a corresponding 51% decrease in power use. Also, an inexpensive 120W TDP CPU air cooler keeps the CPU at a comfortable 48°C. I feel bad limiting the CPU that much. It is like buying a ferrari to drive in city traffic. However, I really appreciate the ability to run two computers for the power use of one.
 2022-01-05, 05:14 #4 VBCurtis     "Curtis" Feb 2005 Riverside, CA 23×661 Posts If the CPU is at 100C and the heatsink is not how enough to burn your finger with extended contact, then heat transfer to the heatsink is failing. Bad thermal paste application (like 5x too thick), or it's seated with a small tilt and only touching the CPU on one side, etc. If the heatsink is way hot, then I'd consider underclocking for the time being while researching cooling further.
 2022-01-05, 05:21 #5 ThomRuley     May 2003 1001000112 Posts Good idea. I'll start by checking the thermal paste. I may have put a little too much on there.
 2022-01-05, 10:31 #6 kruoli     "Oliver" Sep 2017 Porta Westfalica, DE 983 Posts Since you are using task manager, I assume you have Windows? Try HWInfo64. It will show you the CPU package power. If this is a small number (< 100 W, maybe even < 50 W) and it is still throttling, this is very likely a problem with contact. If it has a high number (> 180 W), then the cooling solution might not be sufficient.
2022-01-06, 20:29   #7
ThomRuley

May 2003

3·97 Posts

Quote:
 Originally Posted by Mark Rose Are you overclocking? Which i9 specifically? Air cooling is generally more reliable and cheaper if under you're 200 watts. Because of that, I've never been able to justify the expense of water cooling.
Not overclocking. Just running at factory settings with prime95.
i9-11900K, 3.5Ghz

2022-01-06, 22:08   #8
sdbardwick

Aug 2002
North San Diego County

23·7·13 Posts

Quote:
 Originally Posted by ThomRuley Not overclocking. Just running at factory settings with prime95. i9-11900K, 3.5Ghz
My 11900K runs at 89C max in a 77F(25C) ambient environment using a Noctua NH-U1S Redux (single fan) cooler. Quite pleased with the performance and quality of that $50 HSF; now my go to HSF rather than the CoolerMaster 212 EVO. ETA: Non-OC; runs all cores at 4.7GHz, with CPU package power of 201 Watts. Last fiddled with by sdbardwick on 2022-01-06 at 22:24 Reason: Corrected MAX temp. more info 2022-01-06, 22:17 #9 ThomRuley May 2003 4438 Posts Quote:  Originally Posted by sdbardwick My 11900K runs at 89C max in a 77F(25C) ambient environment using a Noctua NH-U1S Redux (single fan) cooler. Quite pleased with the performance and quality of that$50 HSF; now my go to HSF rather than the CoolerMaster 212 EVO.
Something I couldn't seem to find in the installation instructions - which side should the fan be mounted to the heatsink? I thought this was correct so it could blow the warm air toward the case fan. See attached picture
Attached Thumbnails

 2022-01-06, 22:32 #10 sdbardwick     Aug 2002 North San Diego County 23×7×13 Posts Don't know what others deem "correct", but that's the way I mount my fans.
 2022-01-06, 22:42 #11 ThomRuley     May 2003 29110 Posts The other question I had was how do you tell which side of the fan should face the block? Both sides seem to mount equally well to the block.

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