Custom watercooling performance on 7950x

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Hi, a few months ago I got a 7950x CPU and decided to build a custom watercooling loop for it.

My loop consists of:
• Alphacool Eisblock XPX Aurora Edge (Full Brass) water block
• Alphacool NexXxos XT45 360mm Radiator
• Alphacool 13307 Eisbecher (D5 Reservoir-Pump combo)
• Primochill 3/8in ID X 1/2in OD tubing
• 3 Noctua NF-F12 PPC-3000 fans
• Thermal Grizzly Kryonaut Thermal Compound

The only thing I have water cooled is my CPU. Now this might seem to be very overkill for just cooling a CPU (which it is), yet the cooling performance doesn’t seem to be very good. As I write this my CPU temperatures are around 55 - 60°C (5% CPU usage) and the fans are around 300 RPM. These temperatures aren’t that bad the problem is whenever I put the CPU under load. When I put a load on the CPU (over 90% CPU usage) the temperatures immediately go from around 60°C to 85°C or even 90+ °C . Right after the load ends the temperatures jump right back down to 55 - 60°C.

Now I understand that this CPU gets hot. It’s somewhat the reason why I built this overkill custom loop in the first place. I wanted to squeeze out as much performance out of this CPU as possible (and potentially add a GPU to the loop in the future). My main problem is that I don’t understand the sudden spike in temperature under load and the immediate drop-off after. Right after I built the loop I immediately stressed tested my CPU and noticed this and thought my water block wasn’t mounted properly. After remounting it the results didn’t seem to change. In addition, I don’t ever notice much heat coming up from the radiator even when the CPU is under load.

Is this normal for this CPU and watercooling setup? I would expect that my CPU temperatures would slowly increase as the water began to warm up and slowly decrease as it began to cool down but this doesn’t seem to be the case for my system.

Any help or insight would be much appreciated.

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Yes that sounds normal. The IHS is a limiting factor, and these chips have a very high thermal density.

Delidding would help for temperatures (up to 10-15 c i think, there are articles and videos out there)

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Which is totally fine. There is no thermal throttling and the CPU is built for these temperatures. Anything <=95°C is within specs. The CPU is built to boost to 95°C.

I see similar values on my D15 Noctua. Temps recover within a second to 45-55°C. This aggressive boost behavior needs some adjustment to flatten the fan curve, but that’s about it. I personally don’t care for anything <95°C

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Normal, if you want it lower you have to delid or the very least sand down ihs, be sure not to sand past the LGA retention bracket or you’ll have a bad time

5

I should actually make a slight edit if I was to really stress my CPU (such as compiling a Linux Kernel, prime95, etc.) it will hit 95°C which I guess makes sense with this CPU I don’t think there is really a way to avoid that (unless you were running LN2 or a refrigerant).

I guess the only actual improvements to temperatures I could make is to delid it, swap to liquid metal thermal compound, and get the Direct Die Frame (after I delid).

Thanks for y’all’s input and advice : )

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Yeah I probably should flatten the fan curve. It makes no sense for the processor to jump to 95°C and have my fans jump to running at 100% when the water hasn’t really picked up any heat yet.

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If you really want the fan to slowly ramp up, the best way is to set the fan target against water temperature (although fan speed will change depending on ambient), or calculate the delta between pre-radiator intake and the water temperature (aka delta-T) and set the fan against that.

However, if the M/B doesn’t support temperature input, you may need an external controller to do this. On Linux, Aquacomputer Octo/Quadro and Corsair Commander Pro (non-XT) have kernel hwmon support. fan2go can be used to do both setups. (Another alternative is Aquacomputer Aquaero, although it has hwmon, it can do delta calculation/fan curve/PID control autonomously, but initial setup requires Windows.)

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That’s a good idea. I have a B650E Auorus Master and it does have temperature probes for case temperature. I could probably get a temperature sensor fitting for the actual liquid temperature or I could put a probe on the top and bottom of my radiator. As you suggested I could then calculate the △T between the two probes and configure fan speeds based on that.