system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how are smart phones and tablets able to keep getting faster without ever needing a fan, when older computers with the same performance needed big fans?
gpt
The reason for this is that the electronics get smaller. Smaller electronics have less electric resistance, so they're able to do the same work without consuming as much power and therefore also without developing as much heat. Processing power has doubled without increasing power consumption every 18 months on average for the past 40 years. Within the last 10 years, power-to-performance ratio got good enough to allow us to develop phones that are as advanced as we have now.

That said, the CPUs mobile phones and tablets are well behind the performance of laptop and desktop CPUs from the same year. They don't have the same requirements for multitasking and long term performance. A phone isn't pushed to its limits over a long period of time. It loads a website or an app, which consumes a bit of power for a very short time, then the cpu goes back to power saving. 

A desktop computer from 2012 is still more powerful in raw computing performance than a 2017 flagship phone. It's just that mobile phones never need that level of performance to do the tasks a phone typically does.

If you make a mobile phone keep processing at 100% capacity for a long time, it will soon get very warm,and the performance of it will be more and more limited to avoid overheating. 

A laptop or desktop computer, on the other hand, are designed to be able to run at 100% capacity pretty much indefinitely. To achieve this, they require much more extensive cooling solutions, usually with active fans to remove the heat.