An hour after you’ve settled in with your tablet, busy playing a game, it’s still quiet as a mouse but most laptops would be serenading you with the whir of a system fan. Why can tablets forgo a cooling fan?

今天的問答環節是由SuperUser提供的，SuperUser是Stack Exchange的一個分支，是一個由社群驅動的問答網站分組。

問題

超級使用者讀者喬納森對平板電腦和膝上型電腦之間的硬體差異很好奇。他寫道：

I’m curious why a tablet doesn’t need fans but all laptops do, even the cheap and less powerful netbooks. I thought at first it would be that the screen on a tablet is **aller than a laptop, so the graphics chip doesn’t have to be as powerful and so doesn’t generate as much heat. But then the new iPads have retina display which have a much bigger resolution than most laptops.

Then I thought maybe it’s because tablets don’t multitask like laptops can, but some Android tablets can have 2 (at least) apps open at once, and even jailbroken iPads can. While some low end netbooks struggle to run a web browser and word processor.

If you attach a keyboard to tablet you have a laptop, so why do laptops seem to generate disproportionate amounts of heat?

Is the difference between ARM and Intel/AMD chips? If so what is it about the different chip designs that make Intel/AMD produce so much more heat than ARM chips?

讓我們深入研究一下，看看大家對兩者之間的硬體鴻溝有什麼看法。

答案

超級使用者貢獻者Joel Coehoorn提供了對這種劃分的描述：

Tablets don’t need fans because their CPUs (processors) have a different architecture that is more power efficient and doesn’t generate as much waste heat. This is also why they are able to get 10 hours of run-time on a relatively **all battery.

The other side of this, though, is that the tablet processor is no where near as powerful as a laptop processor, even cheap netbooks. This is why, for example, nearly all tablet operating systems absolutely prevent you from running more than one app at a time, and strictly limit what kinds of tasks apps are able to do in the background.

We are seeing some rapid convergence, though… tablet processors are closing the performance gap with each generation, and chip designers are also working to make laptop/desktop processors more and more power efficient.

Chetan Bhargava強調了導致熱量的一些額外硬體因素：

There are three heat generation points in a laptop:

1. Processor 2. Chipset 3. Graphics 4. Power regulators

1-3 of the above subsystems work at very high speeds. Because these subsystems are clocked so high, the power requirement is very high. High speed and hi power requirements generate a lot of heat in Si. Also, these subsystems use PCIe to communicate and PCIe needs to be clocked to a certain frequency to operate. Multiple PCIe lanes originate from the chipset therefore increasing the power usage and generating heat.

Tablets don’t use high end processors or graphic subsystems. Most of them use ARM core that was developed for embedded market. Such processors don’t use special chipsets or PCIe bus and are not clocked at high speeds as the laptop processors. Hence they don’t generate as much heat.

最後，值得一提的是，並不是所有的膝上型電腦都有散熱風扇，許多當前一代的超極本都有超小型的外形、低功耗的部件（如固態硬碟），並且使用了不依賴風扇的散熱技巧。

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