Comparison Scythe Mugen 5 Rev.B vs Scythe Ninja 5

A feature found in some active CPU coolers (see "Intended Use").

For tower arrangements in general, see Airflow Blowing below. And the double-tower design means that the cooler has two working blocks — that is, two fans and two radiators. Accordingly, there are more heat pipes in the design than in single-tower models — at least 4 of them, and more often 5 – 6 or even more. Such an arrangement can significantly increase the cooling efficiency; on the other hand, it also significantly affects the dimensions, weight and price.

The number of fans in the design of the cooling system. More fans provide higher efficiency (all else being equal); on the other hand, the dimensions and the noise generated during operation also increase accordingly. Also, note that other things being equal, a smaller number of large fans is considered more advanced than numerous small ones; see "Fan diameter" for details.

The highest speed at which the cooling system fan is capable of operating; for models without a speed controller (see below), this item indicates the nominal rotation speed. In the "slowest" modern fans, the maximum speed does not exceed 1000 rpm, in the "fastest" it can be up to 2500 rpm and even more.

Note that this parameter is closely related to the fan diameter (see above): the smaller the diameter, the higher the speed must be to achieve the desired airflow values. In this case, the rotation speed directly affects the level of noise and vibration. Therefore, it is believed that the required volume of air is best provided by large and relatively "slow" fans; and it makes sense to use "fast" small models where compactness is crucial. If we compare the speed of models of the same size, then higher speeds have a positive effect on performance, but increase not only the noise level, but also the price and power consumption.

The maximum airflow that a cooling fan can create; measured in CFM — cubic feet per minute.

The higher the CFM number, the more efficient the fan. On the other hand, high performance requires either a large diameter (which affects the size and cost) or high speed (which increases the noise and vibration levels). Therefore, when choosing, it makes sense not to chase the maximum air flow, but to use special formulas that allow you to calculate the required number of CFM depending on the type and power of the cooled component and other parameters. Such formulas can be found in special sources. As for specific numbers, in the most modest systems, the performance does not exceed 30 CFM, and in the most powerful systems it can be up to 80 CFM and even more.

It is also worth considering that the actual value of the air flow at the highest speed is usually lower than the claimed maximum; see Static Pressure for details.

The maximum static air pressure generated by the fan during operation.

This parameter is measured as follows: if the fan is installed on a blind pipe, from which there is no air outlet, and turned on for blowing, then the pressure reached in the pipe will correspond to the static one. In fact, this parameter determines the overall efficiency of the fan: the higher the static pressure (ceteris paribus), the easier it is for the fan to “push” the required amount of air through a space with high resistance, for example, through narrow slots of a radiator or through a case full of components.

Also, this parameter is used for some specific calculations, however, these calculations are quite complex and, usually, are not necessary for an ordinary user — they are associated with nuances that are relevant mainly for computer enthusiasts. You can read more about this in special sources.

The total time that a cooling fan is guaranteed to run before it fails. Note that when this time is exhausted, the device will not necessarily break — many modern fans have a significant margin of safety and are able to work for some more period. At the same time, it is worth evaluating the overall durability of the cooling system according to this parameter.

The direction in which the active cooler (see "Type") airflow exits.

This parameter is relevant primarily for models used with processors, but the options can be as follows:

— Sideways (scattering). Operation format typical for coolers of the so-called tower design. In these models, the fan is mounted perpendicular to the substrate in contact with the processor, due to which the airflow moves parallel to the motherboard. This ensures maximum efficiency: the heated air does not return to the processor and other system components, but is dissipated in the case (and almost immediately goes outside if the computer has at least one case fan). The main disadvantage of this option is the large height of the structure, which can make it difficult to place it in some system units. However, in most cases this point is not fundamental — especially when it comes to a powerful cooling system designed for an advanced system with a performant "hot" processor. So, it is side dissipation that is the most popular option nowadays — especially in coolers with a maximum TDP of 150 W and higher (although more modest models often use this layout).

— Down (to the motherboard). This format of operation allows you to "lay" the fan with a heatsink flat on the motherboard, significantly reducing the height of the entire cooler (compared to models using side blowing). On the other hand, this form...at of work is not very efficient — after all, before dissipating through the case, hot air again blows over the board with the processor. So nowadays, this option is relatively rare, and mainly in low-power coolers with an acceptable TDP of up to 150 W. And you should pay attention to such models mainly when there is little space in the case and a small cooler height is more important than high efficiency.

The standard noise level generated by the cooling system during operation. Usually, this paragraph indicates the maximum noise during normal operation, without overloads and other "extreme".

Note that the noise level is indicated in decibels, and this is a non-linear value. So it is easiest to evaluate the actual loudness using comparative tables. Here is a table for values found in modern cooling systems:

20 dB — barely audible sound (quiet whisper of a person at a distance of about 1 m, sound background in an open field outside the city in calm weather);
25 dB — very quiet (normal whisper at a distance of 1 m);
30 dB — quiet (wall clock). It is this noise that, according to sanitary standards, is the maximum allowable for constant sound sources at night (from 23.00 to 07.00). This means that if the computer is planned to sit at night, it is desirable that the volume of the cooling system does not exceed this value.
35 dB — conversation in an undertone, sound background in a quiet library;
40 dB — conversation, relatively quiet, but already in full voice. The maximum permissible noise level for residential premises in the daytime, from 7.00 to 23.00, according to sanitary standards. However, even the noisiest cooling systems usually do not reach this indicator, the maximum for such equipment is about 38 – 39 dB.

The type of contact between the heat pipes provided in the heatsink of the cooling system and the cooled components (usually the CPU). For more information about heat pipes, see above, and the types of contact can be as follows:

— Indirect. The classic version of the design: heat pipes pass through a metal (usually aluminium) base, which is directly adjacent to the surface of the chip. The advantage of such contact is the most even distribution of heat between the tubes, regardless of the physical size of the chip itself (the main thing is that it should not be larger than the sole). At the same time, the extra piece between the processor and the tubes inevitably increases thermal resistance and slightly reduces the overall cooling efficiency. In many systems, especially high-end ones, this drawback is compensated by various design solutions (primarily by the tightest connection of the tubes with the sole), but this, in turn, affects the cost.

— Direct. With direct contact, the heat pipes fit directly on the cooled chip, without an additional sole; for this, the surface of the tubes on the desired side is ground down to a plane. Due to the absence of intermediate parts, the thermal resistance at the places where the tubes fit is minimal, and at the same time, the radiator design itself is simpler and cheaper than with indirect contact. On the other hand, there are gaps between th...e heat pipes, sometimes very large — as a result, the surface of the serviced chip is cooled unevenly. This is partly offset by the presence of a substrate (in this case, it fills these gaps) and the use of thermal paste, however, in terms of uniformity of heat removal, direct contact is still inevitably inferior to indirect contact. Therefore, this option is found mainly in inexpensive coolers, although it can also be used in fairly performant solutions.