Following an initial look at thermal compound spread on AMD’s Threadripper 1950X, we immediately revisited an old, retired discussion: Thermal paste application methods and which one is “best” for a larger IHS. With most of the relatively small CPUs, like the desktop-grade Intel and AMD CPUs, it’s more or less been determined that there’s no real, appreciable difference in application methods. Sure – you might get one degree Centigrade here or there, but the vast majority of users will be just fine with the “blob” method. As long as there’s enough compound, it’ll spread fairly evenly across Intel i3/i5/i7 non-HEDT CPUs and across Ryzen or FX CPUs.
Threadripper feels different: It’s huge, with the top of the IHS measuring at 68x51mm, and significantly wider on one axis. Threadripper also has a unique arrangement of silicon, with four “dies” spread across the substrate. AMD has told us that only two of the dies are active and that it should be the same two on every Threadripper CPU, with the other two being branded “silicon substrate interposers.” Speaking with Der8auer, we believe there may be more to this story than what we’re told. Der8auer is investigating further and will be posting coverage on his own channel as he learns more.
Anyway, we’re interested in how different thermal compound spreading methods may benefit Threadripper specifically. Testing will focus on the “blob” method, X-pattern, parallel lines pattern, Asetek’s stock pattern, and AMD’s recommended five-point pattern. Threadripper’s die layout looks like this, for a visual aid:
Because of the spacing centrally, we are most concerned about covering the two clusters of dies, not the center of the IHS; that said, it’s still a good idea to cover the center as that is where the cooler’s copper density is located and most efficient.
Our video version of this content uses a sheet of Plexiglass to illustrate how compound spreads as it is applied. As we state later in the video, this is a nice, easy mode of visualization, but not really an accurate way to show how the compound spreads when under the real mounting force of a socketed cooler. For that, we later applied the same NZXT Kraken X62 cooler with each method, then took photos to show before/after cooler installation. Thermal testing was also performed. Seeing as AMD has permitted several other outlets to post their thermal results already, we figured we'd add ours to the growing pool of testing.
We've got a new thermal paste applicator tool that'll help ensure consistent, equal spread of TIM across cooler surfaces for future tests. As we continue to iterate on "Hybrid" DIY builds, or even just re-use coolers for testing, we're also working to control for all reasonable variables in the test process. Our active ambient monitoring with thermocouple readers was the first step of that, and ensures that even minute (resolution 0.1C) fluctuations in ambient are accounted for in the results. Today, we're adding a new tool to the arsenal. This is a production tool used in Asetek's factory, and is deployed to apply that perfect circle of TIM that comes pre-applied to all the liquid cooler coldplates. By using the same application method on our end (rather than a tube of compound), we eliminate the chance of users changing application methods and eliminate the chance of applying too much or too little compound. These tools ensure exactly the same TIM spread each time, and mean that we can further eliminate variables in testing. That's especially important for regression testing.
This isn't something you use for home use, it is for production and test use. When cooling manufacturers often fight over half a degree of temperature advantage, it would be unfair to the products to not account for TIM application, which could easily create a 0.5C temperature swing. For consumers, that's irrelevant -- but we're showing a stack of products in direct head-to-head comparisons, and that needs to be an accurate stack.