Overclocking, Cooling & Temperature
The Right Cooling Solution
AMD doesn't use thermal paste between the Ryzen Threadripper processors’ dies and integrated heat spreader. Instead, it went with good old solder. This decision should prove critical during our overclocking efforts.
Most reviewers (us included) received all-in-one liquid coolers for their Threadripper CPUs. They're made by Thermaltake and include a flat 360mm radiator with three 120mm fans.
Fully assembled, and sitting next to the motherboard and RGB-lit memory sticks, the whole kit lights up like a Christmas tree. At least it was (almost) fully functional. The only exception was the original thermal paste on Asetek's pump. There was simply not enough of it. Even without overclocking, AMD’s new processor can hit 180W under heavy load, and its heat spreader is relatively large. This combination requires a different approach. Instead of the usual centered blob, we drew a thick line with the thermal paste. We then put the pump in place and gently rotated it back and forth while manually applying some pressure. Only then did we screw it in place.
Installing Your Own Water Cooler
We’ve already reported how AMD changed its interface for Socket TR4 (SP3r2). One of the most important alterations involves the screws. AMD went with M3.5 screws, an uncommon size with a fine thread. You won’t find these at your local hardware store. The difference can easily be spotted in the picture below, with our purchase on the left and an original AM4 screw on the right:
Simply shipping brackets of a different size won’t do the trick here. The acquisition of suitable screws is also necessary. The socket’s threads don’t go all the way through, which is to say that they aren’t open in the back. So, the screws also need to be of the correct length. We tried 20mm screws, and they turned out to be too long. Then we experimented with fitting spacers. A good length for the screws would have been 15mm, but this might vary depending on the bracket’s thickness.
The next question, which is even more important than the first one, is how much pressure to apply. We used a special torque wrench with very small steps and M3.5 screws with internal hexagonal threads, and started with a reasonable 0.1Nm. From approximately 0.25Nm, we couldn’t detect any further gains in cooling performance, so that's where we stopped. A sensible maximum pressure is approximately 0.35Nm.
The picture below shows our completely installed cooling solution. The CPU block’s an Alphacool XPX with a bracket for AMD’s Socket TR4 (SP3r2). The polyamide washers are used as spacers and take the place of springs. The top washers are made of steel to keep the head of the cylinder from boring into the much softer washer material during the CPU block’s installation.
Our Ryzen Threadripper 1950X sample overclocked to 3.9 GHz and 1.35V. However, the all-in-one water cooling solution in our kit couldn’t keep the system stable at that level. This was due to the processors’ power consumption rising to more than 250W during rendering.
And so we went back to our Chiller to achieve some better comparisons. This way, there’s one true constant to our measurements: a water temperature of approximately 20°C, which can be held constant, even topping more than 300W of waste heat.
For everyday use, a normal water-cooling solution will definitely suffice thanks to the soldered heat spreader, which makes AMD’s processor much less of a challenge than Intel's Core i9-7900X. Our approach simply allows us a bit more sophistication in our overclocking endeavors.
Using the Chiller, AMD’s Ryzen Threadripper 1950X achieved 4 GHz at 1.45V. Just don't expect to see those results from your own overclock. Even the Chiller started to fall behind the CPU's thermal output as temperatures crept too high for comfort. This is why the processor is overclocked to more reasonable levels for our benchmarks, with Threadripper running at 3.9 GHz.
Maximum Temperatures: Stock Clock Rate
AMD circulated a 27°C addition to the Tctl values, which is supposed to amount to the average core temperature. This sounds about right to us after taking a look at the temperature difference between Tctl and Tdie (the latter being the chip temperature). Between this and the fact that a huge cooler made it practically impossible to conduct our own heat spreader measurements, we're forgoing the delta measurements you saw in our Ryzen 3, 5, and 7 reviews.
We stick with the water cooling solution that AMD provided for our first results. As a bit of a power consumption spoiler, the motherboard limits the two CPUs between 179 and 180W. This upper boundary can’t even be exceeded for short periods of time using normal motherboard settings.
Here are the temperature curves:
The CPU temperature values reported by HWInfo64 through Asus' separate sensor loop are between 6°C and 12°C lower than the Tctl values, and they rise more slowly. The voltage converter temperatures of just under 60°C, achieved without any additional cooling, are great.
Maximum Temperatures: Overclocked
Increasing voltages to guarantee stable operation pushes the processor well beyond its sweet spot. Consequently, power consumption goes through the roof. Operating well beyond 300W poses a challenge for any cooling solution. That's why we're using the Chiller. We did try a normal water-cooling loop though, resulting in the Tctl and Tdie values going up by ~10°C to 15°C. This is well within an acceptable range.
The overclocked 1950X peaks at a hefty 320 to 325W. Using the Chiller, this level of power consumption is accompanied by Tctl values of 87°C. That’s actually not as severe as it seems once the offset and Tdie values are taken into account. A real temperature of approximately 60°C serves as a great demonstration of why solder is superior to thermal paste. Intel's Core i9-7900X could have had so much potential if the company hadn't taken the easy way out.
Voltage Converter Temperatures
We’ll conduct a separate test with different loads and X399 motherboards in the future. As for the Asus X399 ROG Zenith, its voltage converters generally stay under 100°C without any additional air cooling, even as AMD's CPU consumes well over 300W.
Asus set its throttling temperature threshold to 105°C. Even a bit of airflow helps, though. This is demonstrated quite nicely by the temperature curves for the overclocked configuration above. The fan that’s installed right above the I/O shield doesn’t really have any effect, unless you count its unnecessarily high noise level. Asus should have done without this gimmick.
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