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Why it matters: YouTuber der8auer conducts an interesting experiment, testing a passive cooler with Intel's Core i9-9900K CPU. It's not exactly what I'd call a "real-world" test and it's far from what you could expect with a 100 percent passively cooled system in an enclosed chassis but it's an interesting experiment nevertheless.
There are many approaches to take when building a PC. At the top of my list of priorities is silence. My current system consists of mid-range (for its time) hardware in an oversized case outfitted with large, slow-spinning fans and a solid state drive. There's a massive twin-tower heatsink on the CPU that's overkill for all but the highest-end of chips. The rig is still audible, but just barely.
While still sufficient for my needs, I've dreamed of building a truly high-end rig that is entirely passively cooled. Maybe I'll get around to it someday but in the meantime, I can enjoy watching others do the same.
YouTuber der8auer recently set about to testing the Arctic Alpine 12, a passive heatsink made from a single chunk of aluminum. Visually, the heatsink is nothing to write home about. In fact, it looks more like an old-school cooler than something you'd use to cool a modern CPU... much less, an Intel Core i9-9900K.
In fairness, this isn't really the passively cooled system of my dreams (nor is der8auer making it out to be). The system isn't mounted inside a case but rather, sits out in the open air. The video card also has a fan on it and the Seasonic PSU also appears to be actively cooled. Still, he's using a fanless heatsink rated to handle a TDP of just 47W to cool an i9-9900K.
Sitting at the desktop in Windows, the average CPU core temperature was around 49 degrees Celsius but when running Cinebench R20, it immediately shot up to around 100C. Further stress testing with Prime 95 revealed the chip is being throttled down to around 2,600MHz with power consumption of just 54W.
With a bit of manual tweaking in the BIOS, der8auer was able to run Far Cry 5 at 1080p with an Nvidia GTX 1050 Ti at around 40 frames per second with a CPU frequency of 3.6GHz at 0.925v. CPU utilization while playing hovered between 15 to 30 percent. CPU temps stayed around 70C to 75C.