RTX 4090 FE's Axial Fans Are Also Great at Cooling CPUs

PC (Image credit: Chiphell)

Have you ever wondered how those axial fans from Nvidia's GeForce RTX 4090 or GeForce RTX 4080 Founders Edition perform outside the graphics card? One DIY enthusiast from the Chiphell forums (via Olrak) has the answer, as he has repurposed the axial fan from two of the best graphics cards for his top-down CPU cooler and shared the results.

The axial cooling fan seemingly kept the forum member's Core i5-13600KF's operating temperature up to nine and five degrees Celsius lower than the Thermalright TL-C12 and Cooler Master Mobius 120P ARGB, respectively, during the Cinebench R23 benchmark. In addition, the noise level was reportedly lower than the other fans during regular operation. However, the axial fan emitted a humming noise at very low RPMs, making it more audible than other 120mm and 90mm he had tested.

Nvidia utilizes a combination of Nidec's AD4A31K04 and AD4A31K05 cooling fans for the company's GeForce RTX 40-series (Ada Lovelace) Founders Editions graphics cards. Nidec Servo, the Japanese manufacturer's subsidiary, gained much fame for developing the renowned Gentle Typhoon fans in 2009. With such a distinguished pedigree, it's easy to understand why Nvidia chose Nidec to provide the active cooling solution for Founders Edition products.

The AD4A31K04 and AD4A31K05 are similar in their core, but there's a difference in the airflow direction. Remember that Nvidia employs a dual-axial fan design for pushing air in different directions. Sellers have labeled the fans as Type A and Type B. The former pushes the air toward the front of the blades, whereas the latter directs the air in a downward direction to the motor. 

The fans typically retail for $20 on Chinese online platforms like AliExpress or Taobao. However, merchants on the latter sell the fans for less than $1.50 — I kid you not. The laughably low price tag allows DIYers to experiment with the AD4A31K04 and AD4A31K05 beyond the product's original use scope.

The problem is that Nidec has tailored the cooling fans to Nvidia's specifications. They don't come with a standard 120mm design; therefore, the mounting holes are different. Furthermore, the AD4A31K04 and AD4A31K05 aren't even 120mm cooling fans. According to one Taobao merchant, they measure 115 x 115 x 12.5mm, so DIYers have to 3D print their own bracket out of plastic or some other type of material. It's a challenge, as another Chiphell forum user stated that the fan's diameter measures 116m with around 2mm of reserved space. As a result, the frame's thickness is limited to 1mm.

Nidec doesn't list the AD4A31K04 or the AD4A31K05 on the company's website, so we gathered the specifications from the various Chinese merchants around the market. The fan's base is metal, while the motor's shell is made from aluminum alloy. The fan has a maximum speed of 3,300 RPM and can pull up to 0.63A. However, one owner claims that some samples can hit 3,500 RPM. In any event, the AD4A31K04 and AD4A31K05 are very fast-spinning fans. 

They do have a substantial power draw, though. The Cooler Master Mobius 120P ARGB has all the disco lights and is rated for 0.48A, and the AD4A31K04 and AD4A31K05 are up to 31% higher. This isn't a big issue since conventional 4-pin fan connectors are suitable for up to 1A.

The AD4A31K04 or the AD4A31K05 draws power from a special ribbon cable with a six-pin layout. While the fans connect directly to Nvidia's PCB, they require a custom 4-pin adapter to connect to a standard fan connector on the motherboard.

Given the overall cost and complexity of modding the axial fan, purchasing a premium cooling fan for your CPU cooler, AIO liquid cooler, or case is probably more viable. Still, it's always cool to see DIYers think outside the box.

Zhiye Liu
RAM Reviewer and News Editor

Zhiye Liu is a Freelance News Writer at Tom’s Hardware US. Although he loves everything that’s hardware, he has a soft spot for CPUs, GPUs, and RAM.