Billet Labs builds fanless GeForce RTX 5080 PC, coolant hits 60°C
Billet Labs has returned with another retro/steampunk styled PC build. This time they built a fanless gaming PC with a GeForce RTX 5080 and Ryzen 7 9800X3D. The system uses passive water cooling, three radiators and polished copper piping, but the test shows how difficult it is to cool modern gaming hardware without airflow.
This is a follow-up to the company’s earlier Victorian radiator PC project That system used a 50 kg cast-iron radiator, but it was not a fully passive PC. It still had fans and required regular maintenance due to pump and filter issues.
RTX 5080 runs without GPU throttling
The new build uses a Gigabyte AORUS Pro B850 motherboard, 32GB of memory, 2TB of storage and a 600W Flex ATX power supply. Cooling is handled by 120×240 mm, 140×280 mm and 200×400 mm radiators stacked above the components to use natural convection.
Source: Billet Labs
Billet Labs also tried to remove the small motherboard fans from the equation. The motherboard was mounted on an 8 mm aluminum base plate, with thick thermal pads used to transfer heat from the board into the base. The power supply was also mounted with thermal paste underneath to help dump heat into the same plate.
The system worked at idle, with the coolant temperature stabilizing at around 28°C. In Cinebench, the Ryzen 7 9800X3D pulled more than 130W, while the coolant reached around 39°C after roughly half an hour. CPU core temperatures averaged just under 90°C.
Source: Billet Labs
Under gaming and GPU-heavy loads, the coolant temperature climbed much further. FurMark pushed the coolant to around 53°C, while Cyberpunk 2077 raised it to around 55.5°C. The GeForce RTX 5080 did not throttle during these tests, but the coolant was already too hot for comfortable long-term use.
CPU throttles before the GPU does
The worst result came from running Cinebench and FurMark at the same time. The coolant eventually reached 60°C, the CPU started throttling and the power supply fan became audible. The RTX 5080 was still operating without throttling, but the system no longer met the goal of a practical passive gaming PC.
Source: Billet Labs
Billet Labs concluded that the build technically worked, but not well enough for daily use in this form. Still, it still looks interesting…
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