Passive cooling is always a problem for high performance. This is shown, for example, by comparative tests of the MacBook Air and Pro, where the former is passively cooled, and even under prolonged load, even the otherwise economical Apple M2/M3 processors cannot avoid throttling, i.e. limiting performance by e.g. reducing the frequency. In the case of phones, it’s even more striking, passive cooling is standard there, the space for cooling is small, so the problems with maintaining performance without the above-mentioned reduction in clocks can be even greater. And this is something that plagues many powerful mobile processors. One of the recent tests showed this on the CPU MediaTek Dimensity 9300. This processor gets a standing ovation for its very high performance. In order not to, when it has 4 Cortex-X4 cores (one at 3.25 GHz, the other three at 2.85 GHz), it also has four Cortex-A720 with a frequency of 2.0 GHz, which take over the role of energy-saving cores (instead of A5x0, which this processor does not have at all). In benchmarks, this monster surpasses the Snapdragon 8 Gen 3 and literally makes fun of the Apple A17 Pro in multi-threaded performance. But when it comes to consumption, it’s a bit of a problem.
The above-mentioned test, which we will now look at in more detail, is not a very good example of real deployment, so it needs to be taken as the worst possible case and the reality will be better on average, on the other hand, it is an interesting probe for such extreme cases. On an 8-core processor, it launched 100 computing threads. During the first 3 minutes, the processor hovered above 90% of the maximum power, but then the power dropped and remained somewhere slightly above 75% until about the 9th minute. It then dropped below 70% power and at 12 minutes even lower. The result was even a drop to 46% of the maximum performance that the processor is capable of, which means less than half.
The clock of individual cores dropped to 1.5 GHz in three cases, another four ran at 1.2 GHz and one core even reduced its clock to 0.6 GHz. The phone was here
Vivo X100 Pro, which has fairly solid cooling using a vapor chamber. But again, it is good to remember that this was an extreme test, which may not correspond very well to reality. MediaTek defends that the Dimensity 9300 actually achieves much better peak and average performance than the competition when tested properly. There was no comparison with the competition here.
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