Why do laptops need fans but tablets don't?

Question

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 smaller 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?

Answer 1

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 small 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, or two at most, 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.

Answer 2

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.

Answer 3

Its a matter of design and requirements. Arm processors are really power efficient, but don't have performance to the same level as an x86 in many cases.

For a low power, passively cooked heatsinkless x86, take a look at via's designs, the old AMD geodes or the phone-grade atom processors intel is working on.) TArm processors also run at slower speeds (the fastest phone processors run at about 1.2 ghz I believe with up to 4 cores, with the slowest modern X86 processor at twice that), though thats an apple and oranges comparison - clock speed dosen't compare between processor families (the PIV was outclassed, rather embarassingly by pentium Ms of the era, at half the clockspeed).

Other components may be less powerful as well - phones wouldn't need to handle many storage devices (the early desktop grade atoms had a passively cooled main processor, and a fan for the chipset) so they can be less complex and produce less heat.

Basically each has a different set of compromises (which gradually converge - PCs are becoming more SOClike, while Phones are becoming pocket computing devices, with more complex processors powering them.), Power vs Power efficiency, and complexity and flexibility vs simplicity for a monolithic design.

Answer 4

Older laptops have older processors, which are made with a less advanced, bigger architecture process. Means the transistors are bigger, and generate more heat.

As processors architecture get smaller, they can fit more and more transistors in the same area, since the transistors are smaller themselves.

Right, so tablets and phones, TV's use ARM processors, which is an architecture, just like x86, x64, but designed by another company, made to produce almost no heat waste. And to be energy efficient. This is likely accomplished, because there are less transistors fit tightly, close togther.

ARM is different than most desktop processors, as they have less transistors on the same area.

Answer 5

Basically the race is not so much on speed anymore as on saving power. This is why we have moved on to SSD drives, low powered ARM CPU's and smaller form factors.

Why do laptops generally require more cooling? Because they do more, they can run multiple programs, and have a robust OS that also does more. Tablets and smartphones generally run one app at a time and this prevents the hardware from running too hot. All mobile processors have been designed for their mobile purpose. Many say Apple using mobile chips in the iMac desktops actually degrades performance over the traditional desktop CPU of the same speed. I tend to agree, but Apple must use mobile processors because of the form factor in the iMac's and even Mac Mini. This is really not such a problem anymore and they are like the Chromebook and tablets which can do HD video and high resolutions without much issue. It's because the focus recently in technology of processors has been on mobile ones.

Let's also remember the real reason heat is created is from current draw. As processors, in general, have started requiring less voltage, they have also become cooler. Unless you're a gamer, almost any system and processor today will do web without a problem. It's only those applications like video and photo editing or CAD drawing, where you will need more processing power.

Answer 6

Definitely not all laptops need a fan. I put together a Dell Latitude 2110 netbook which has no case. After installing Windows and downloading the drivers I realized the fan was not running. It's been on and running for hours and the heatsink is no warmer than it was when I clued in. Low end computers can run a word processor and a web browser just fine, they're just not very good at multitasking. Usually the cause for the need of a fan is that the CPU and GPU generate a lot of heat, and they're typically too large to cool off in open air. The newer ARM processors and the Intel Atom processors are much smaller and barely heat up.

Answer 7

I understand the question and the most basic answer is that Laptops generally have more components that generate more heat. Tablets don't have any moving parts like how a laptop's hard drive will generate a lot of heat.

Software efficiency will help with how cool a device runs as well. A program designed for displaying just the normal desktop won't heat things up because it is a low level program but run a high level game or run the GPS program (which I guess counts as the same thing) and you'll see that no matter whether it is a laptop or tablet, it'll run hotter.

Tablets today generally create a lot of heat as well. If you don't believe me, just turn on tablet or smartphone and run your GPS or run a program with a heavy load. Even a Samsung Galaxy phone will heat up within minutes to a uncomfortable temp just running the GPS software. There are SOME exceptions as always to every rule on both the laptop and tablet sides. Take the Trio AXS tablet for example, even compared to other tablets with the same or similar specs. It tends to run far cooler than the competition and all without any fans, even running the GPS or other intense software.

As technology improves and people desire more out of their devices, the lines will continue to blur. Will phones become as powerful as a desktop? Perhaps someday. One thing I do know that unless a breakthrough happens in cooling technology, we will all end up having to deal with having hot, uncomfortable smartphones, tablets, and laptops in our hands.