Only One Fan on the Base 24-inch iMac: What's the Consequence? | MacGeneration

Among the differences between the very first 24-inch iMac, the one sold for €1,449, and the more expensive models, there is also one fan… less. While Apple has equipped its all-in-one with two fans on the majority of its range, the basic model must be satisfied with a single fan placed on the left. On paper, this means that its active cooling is less efficient, which can lead to a drop in performance when temperatures rise too much.

To find out the real impact of this difference, the YouTube channel Max Tech conducted a series of tests with two iMacs, an entry-level model and a version with its two fans. These tests aim to answer two different questions: do we hear more of one of the two Macs? And is the performance reduced because of the missing fan?

To distinguish between the two models effectively, it is necessary to carry out tests over time. The computer will heat up to the point where it will increase the speed of its fan(s) to keep its components at an acceptable temperature. If its cooling system is efficient, it will be able to maintain performance at the highest level by keeping its ventilation active. Otherwise, performance will be reduced while the components cool down: this is called thermal throttling (literally, thermal throttling).

So much for the theory. In practice, the youtuber quickly finds a difference between the two iMacs with the 3DMark WildLife test. The entry-level model quickly exceeds 80° and its fan reaches its maximum speed, becoming clearly audible. The other all-in-one stabilizes around 70° and it does so by keeping its two fans at their base speed, around 2,500 rpm. At this level, it is not possible to hear them without sticking the ear against the computer.

On this test, the difference is above all audible. The performance, on the other hand, was maintained, with a difference of 10% between the two models, which is logical since the entry-level iMac has a GPU with only seven cores, compared to eight for the others. Even though the computer got hotter and its fan was louder, it didn't have a negative impact on performance.

After the GPU, it's time for the CPU, which is identical on both iMacs. This time, the YouTuber uses Cinebench to push the processor to 100% and keep it there over time. And history repeats itself: the base iMac gets up very quickly to more than 90° and its fan quickly reaches its maximum rotational speed, while the more high-end model reaches this temperature more slowly and only needs slightly increase the rotational speed of its fans. The latter remains inaudible, unlike the Mac with a single fan.

This time, there is another difference: the CPU frequency drops on the entry-level iMac, while it remains at 3.2 GHz on the other model. This is a sign of thermal throttling: the processor is throttled to prevent overheating. As a logical consequence, performance is better on the more expensive all-in-one, while the processor is identical on both. But even if the temperature difference is significant and even if the basic iMac is noisier, the difference in performance remains nevertheless measured, around 10% in favor of the better cooled model.

Tests in real conditions, such as video exports made by Max Tech, confirm that the performance differences are small. It's no surprise, we've known since last fall that Macs with the Apple M1 chip have excellent performance in all circumstances, even the fanless MacBook Air. For the most demanding needs, the high-end iMacs are quickly imposed, the price difference is not that significant and will well justify the 10% additional performance.

For most needs, however, any 24-inch iMac will do. What the second fan adds is actually silence. The base model has to activate its fan much earlier and much louder, so it's heard louder and longer. If silence is an important criterion for you, it is better to avoid the cheapest iMac for this reason, even if it is still necessary to remember that in basic use, its fan will not be heard either.

iFixit hasn't dismantled an entry-level 24-inch iMac, but the specialized site still offers this X-ray view which confirms that there is only one fan on the left. A surprising choice of placement, when you consider that the Apple M1 is placed more to the right, half in front of the foot in this photo. Wouldn't it have been wiser to place the fan on the right? The placement chosen by Apple remains quite mysterious…

If you are unsure, you can also (re)read our full review of the 24-inch iMac: