Office Password Recovery Share our experience in deciphering server cooling
Our decryption servers generally use obsolete mining machines, or decryption servers for short (we can't afford professional multi-graphics card servers either. With the hype surrounding AI, graphics cards are very expensive. If we charge the current decryption fee, it probably won't even cover the electricity bill. So we use slag machines that others have obsoleted many years ago to reduce costs).
Now that summer is here, the indoor temperature is above 34°C. The graphics card temperature directly affects the stability and lifespan of the mining machine. For high-density mining rigs with eight graphics cards installed, Negative Pressure is generally more effective than Positive Pressure .
Conclusion first: Negative pressure cooling is recommended.
For multi-graphics card mining rigs, the core issue is not to "blow a cool breeze" on the chassis, but rather to dissipate the huge heat generated by the graphics cards out of the chassis as soon as possible. The negative pressure mode does this most effectively.
1. Negative pressure cooling (exhaust fan > intake fan)
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Principle : The total air volume of the exhaust fan is greater than that of the intake fan, so that the air pressure inside the chassis is slightly lower than the air pressure in the external environment. Outside air is drawn in through all the gaps in the chassis, such as PCIe slot gaps, graphics interface gaps, etc.
Advantages:
Efficiently expels hot air: It can quickly "pump out" the hot air accumulated between the graphics cards, preventing the hot air from stagnating and circulating inside the chassis, which is the key to cooling down.
Optimized for graphics cards: The graphics card itself is designed so that an axial fan sucks air from below and then blows hot air to both sides (especially the end of the I/O baffle and the rear of the graphics card). A negative pressure environment can better assist in the expulsion of this hot air from the rear and top of the chassis.
Avoid heat buildup: For a chassis with 8 cards arranged closely together, positive pressure makes it difficult for airflow to penetrate the narrow gaps between all the graphics cards, which can easily form local high temperature zones. Negative pressure directs the airflow globally, ensuring that the hot air has a clear outlet.
Disadvantages:
More prone to dust accumulation: Because air is drawn in through all unfiltered gaps, dust also enters. It needs to be cleaned more frequently.
2. Positive pressure cooling (intake fan > exhaust fan)
Principle : The total airflow of the intake fan is greater than that of the exhaust fan, making the air pressure inside the chassis higher than that outside, and the internal air will be "pushed" out through various gaps.
Advantages:
Good dustproof effect: If all air intakes are equipped with dust nets, the air entering the chassis is filtered, which can greatly reduce dust accumulation inside.
Disadvantages (fatal to mining machines):
Easily forms hot air vortices: If the incoming cold air is heated by the graphics card and cannot be discharged in time, it will circulate inside the chassis, causing the temperature to gradually rise and the heat dissipation efficiency to drop sharply.
Airflow is difficult to manage: The direction of the positive pressure airflow is uncontrollable, and the cold air may not be able to effectively reach the core area of the graphics card that needs the most heat dissipation, but may instead be blocked near the air intake.
Why is negative pressure more suitable for multi-card mining machines?
Imagine eight graphics cards working side by side:
Each graphics card is generating heat like crazy, and they are themselves a powerful heat source and "blower" (blowing hot air around).
The main task inside the chassis is not "cooling," but "ventilation"—replacing the hot air in the chassis with cold air as quickly as possible.
Negative pressure is like a powerful range hood; it can efficiently suck out fumes (hot air) no matter where you are in the kitchen (inside the chassis).
Positive pressure, on the other hand, is like turning on several electric fans in the kitchen to blow air. Although there is wind, the fumes can easily swirl in the corners and cannot be completely expelled.
Best Practices and Duct Construction Recommendations
Neither negative nor positive pressure is perfect; Constructing a reasonable, exhaust-dominated directional duct is key.
Basic principle:Cold air enters from the bottom/front and hot air is exhausted from the top/rear. Because hot air naturally moves upwards.
Fan configuration:
Air intake: Install 2-3 fans (if there is a case space) at the bottom or front of the chassis, equipped with a dust net. The rotation speed can be set to medium to ensure that there is enough cold air entering.
Exhaust: Installmore, more powerful fans on the top and rear of the chassis. This is the focus of investment. Their total exhaust air volume is significantly greater than the intake air volume, thereby creating negative pressure. It is recommended to use a 120mm or 140mm fan with high airflow.
Auxiliary measures:
Remove excess baffles: Ensure that the space between graphics cards and PCIe slots is unobstructed, facilitating negative pressure air intake and efficient heat dissipation.
Use a graphics card bracket: Maintain consistent spacing between graphics cards to avoid blocking the bottom airflow channel due to graphics card sagging.
Ambient ventilation: Place the mining rig in a well-ventilated environment, not too close to the wall, to ensure that the exhausted hot air can dissipate quickly.
Monitoring and Adjustment:
Closely monitor the GPU Core and GPU Junction Temperature / Memory Junction Temperature of each graphics card using HWiNFO64 or similar software. Memory junction temperature is often the first culprit behind overheating and frequency reduction during mining.
Adjust the fan speed curve according to the temperature conditions. Ideally, the speed of the exhaust fan should increase dramatically as the average temperature of the graphics card rises.
Summary
Preferred option: Construct an exhaust-dominated negative pressure duct. Focus on increasing the power of the exhaust fans at the top and rear.
SECONDARY CONSIDERATION: Install dust screens at air intakes and clean them regularly to balance heat dissipation and dust protection needs.
Absolutely avoid: Positive pressure is formed, or the intake and exhaust fans have equal airflow, resulting in a lack of clear air ducts (this will cause hot air to move around wildly, which is 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.