Share our experience in deciphering server cooling

2025-09-03 15:44:11

Our decryption server generally uses the eliminated mining machine, the decryption server is referred to as the mining machine (we can't afford to buy a professional multi-graphics card server, AI is hot, graphics card is very expensive, if you charge according to the current decryption, I am afraid that even the electricity bill is not enough, so we use the slag machine eliminated by others many years ago to reduce costs)

Now that summer is here, the indoor temperature is above 34°, and the temperature of the graphics card is directly related to the stability of the mining machine and the life of the graphics card. For high-density miners with 8 graphics cards, negative pressure is usually better than positive pressure.

Conclusion First: negative pressure heat dissipation is recommended

For multi-graphics card miners, the core problem is not to "blow cool air" on the chassis, but to expel the huge heat generated by the graphics card out of the chassis as soon as possible. The negative pressure mode does this most effectively.

1. Negative pressure cooling (exhaust fan > intake fan)

• Principle: The total air volume of the exhaust fan is greater than that of the inlet fan, so that the internal air pressure of the chassis is slightly lower than the external ambient air pressure. External air is drawn in from all gaps in the chassis (e.g., PCIe slot gaps, graphics card interface gaps, etc.).

• Pros:

• Efficient hot air exhaust: It can quickly "pump out" the hot air collected between the graphics cards to avoid stagnant circulation of hot air in the chassis, which is the key to cooling down.

• Optimized for graphics cards: The graphics card itself is designed with an axial fan drawing air from below and then blowing hot air to both sides (especially the IO bezel end and tail of the graphics card). The negative pressure environment better assists in the evacuation of this hot air from the rear and top of the chassis.

• Avoid heat buildup: For a case with 8 cards closely arranged, it is difficult for positive pressure to allow airflow to penetrate the narrow gaps between all graphics cards, which can easily form local high temperature zones. Negative pressure guides the direction of the airflow from the overall perspective, ensuring that the hot air has a clear outlet.

• Cons:

• Dust buildup is more likely: because air is drawn in through all unfiltered gaps, and dust enters with it. Needs to be cleaned up more often.

2. Positive pressure cooling (intake fan > exhaust fan)

• Principle: The total air volume of the inlet fan is greater than that of the exhaust fan, so that the air pressure inside the chassis is higher than the outside, and the internal air will be "pushed" out through various gaps.

• Pros:

• Good dust prevention effect: If all air inlets are installed with dust screens, then the air entering the chassis is filtered, which can greatly reduce internal dust accumulation.

• Disadvantages (fatal to miners):

• Easy to form hot air vortices: After the incoming cold air is heated by the graphics card, if it cannot be discharged in time, it will circulate in the chassis, resulting in a gradual increase in temperature and a sharp decrease in heat dissipation efficiency.

• Airflow is difficult to manage: The direction of positive pressure airflow is uncontrollable, and cold air may not effectively reach the core area of the graphics card that needs to dissipate the heat, but is blocked near the air inlet.

Why is negative pressure better for multi-card miners?

Imagine 8 graphics cards working side by side:

1. Every graphics card is producing heat like crazy, and they are a powerful source of heat and a "blower" (blowing hot air around).

2. The main task in the chassis is not to "cool", but to "ventilate" - to replace the hot air in this case with cold air as quickly as possible.

3. Negative pressure is like a powerful range hood, it efficiently sucks away fumes (hot air) no matter where you are in the kitchen (inside the chassis).

4. The positive pressure is like turning on a few electric fans in the kitchen to blow the air, although there is also wind, but the oil fumes are easy to hover in the corners and cannot be completely discharged.

Best practices and air duct construction recommendations

Pure negative pressure or positive pressure is not perfect, and building a reasonable exhaust-led directional air duct is the key.

1. Basic principle: cold air inlet at the bottom/front, hot air exhausted at the top/rear. Because hot air naturally goes upwards.

2. Fan configuration:

• Air intake: Install 2-3 fans at the bottom or front of the chassis (if the chassis is located), equipped with dust screen. The rotational speed can be set to medium, ensuring that there is enough cool air to enter.

• Exhaust outlets: Install more and more powerful fans on the top and rear of the case. This is the focus of the investment. Their total exhaust air volume is significantly greater than the air intake, so as to form negative pressure. It is recommended to use a 120mm or 140mm fan with high air volume.

3. Ancillary measures:

• Remove excess bezels: Ensure clear space between graphics cards and PCIe slots for negative pressure suction and efficient heat dissipation.

• Use a graphics card bracket: Keep the spacing between graphics cards consistent to avoid blocking the bottom airflow channel due to sagging graphics cards.

• Ambient ventilation: Place the miner in a well-ventilated environment, not too close to the wall, to ensure that the exhausted hot air can dissipate quickly.

4. Monitoring and Adjustment:

• Use HWiNFO64 or similar software to closely monitor the core temperature (GPU Core) and memory junction temperature (GPU Junction Temperature / Memory Junction Temperature) of each graphics card. The memory junction temperature is often the first culprit of overheating and frequency reduction during mining.

• Adjust the fan speed curve according to the temperature situation. Ideally, the speed of the exhaust fan should increase sharply as the average temperature of the graphics card increases.

summary

• Preferred solution: Construct a negative pressure air duct dominated by exhaust. Focus on strengthening the exhaust fan power at the top and rear.

• Secondary consideration: Install dust screens at air inlets and clean them regularly to balance heat dissipation and dust protection needs.

• Absolutely avoid: positive pressure is formed, or the air volume of the inlet and exhaust fans is equal, resulting in no clear air duct (this will cause hot air to run around, the worst effect).

By optimizing the negative pressure air duct, you can significantly reduce the operating temperature of your graphics card, thereby improving computing power stability and extending the lifespan of expensive graphics cards.