Is 240mm AIO Enough for 5800X3D?

Yes, a 240mm AIO can be sufficient for the Ryzen 7 5800X3D, but with several key factors to consider:

Heat Dissipation and Power Consuming
With 105W TDP (Thermal Design Power) and the 3D V Cache layer, it’s higher thermal resistance and makes it harder to dissipate heat than standard CPUs. However, the chip itself isn’t a huge power consumer, and the 240mm AIO is capable of dissipating around 330W (depending on the model) in most cases. According to the discussions, this heat transfer limit may not result in significant improvement in cooling performance if we used a big radiator (such as a 360mm AIO).

Thermal Resistance and Cooling Efficiency
The 5800X3D isn’t actually power hungry; the issue is the thermal resistance added to the 3D cache, resulting in poor cooling efficiency. That will mean even with a 240mm AIO, the CPU will likely run hotter than you’d expect, especially under full load. Users in the forums, however, point out that temperatures like this aren’t unusual for Zen 3D chips, so so long as the system does not thermal throttle, the temperatures are fine.

Users Experience

Another user had reported idling at 71°C, much higher than we expect. Ambient conditions dictate the normal idle temperatures closer to 35-50°C. Which leads me to believe there is an issue with the AIO setup rather than there being a capacity issue with the 240mm AIO itself (air flow, pump is not working correctly, bad thermal paste application).

Case and Airflow considerations
Several factors beyond the radiator size can affect cooling efficiency:

1. Radiator Positioning: By installing the 240mm AIO as over-exhaust at the top of the case, it can draw in and pull warm air from the system causing cooling performance to drop. It can be installed as an intake to cool with cooler outside air.
2. Airflow and Case Design: The intake and exhaust fans have to be good, and there has to be good airflow in the case. Badly ventilated case can also result in higher overall system temperatures, which makes it harder for AIO to do the job well itself.
3. Pump and Fan Speed
Fan and pump speeds affect how you can maximize the performance of your 240mm AIO. Ensure that:

• The speed of the pump is 100%.
  With temperature increases fans are set to ramp up appropriately. During heavy loads, high performance fans can help keep temps down.

Finally, for the Ryzen 7 5800X3D, I’d say that a 240mm AIO should be enough, given proper installation, proper airflow and working pump. The 5800X3D should be fine to cool with the 240mm, and expect higher-than-usual temperatures compared to non-3D Ryzen chips, but unless you’re hitting thermal throttling (which typically occurs around 90-95°C) the 240mm should be able to handle the load. If your idle or load temperatures are way out of whack, it may be that the cooler isn’t the problem but that the installation is.

If you need extra cooling headroom, or plan to do heavy sustained workloads, upgrading to a 280mm AIO may be a marginal improvement, whereas a 360mm AIO is probably overkill and unnecessary unless you’re in extreme conditions or overclocking.

Table: Cooling Performance Analysis for Ryzen 7 5800X3D with 240mm AIO vs. Alternatives

My Personal Recommendations
For most people, a 240mm AIO will suffice for the Ryzen 7 5800X3D unless you are going to overclock it. It operates at normal temperatures but gets closer to higher temperatures (85-90°C) under prolonged and intense loads or in a hot climate.

A 280mm AIO cools as effectively as a 240mm but at a significantly lower noise-level and therefore qualifies as an upgrade if the case supports it. It provides more headroom especially for the people who want to guarantee the lower temperatures for the constant boost clocks.

A 360mm AIO is the most suitable if you want the highest performance of your CPU and if you run heavy workloads or live in a hot climate. It almost eliminates the feature of thermal throttling, which results in the effective boost frequencies of the CPU.

High-End Air Coolers can be an option but they may fail to handle heat density of Ryzen 7 5800X3D’s 3D V-Cache particularly at multi-core loads.