More and more phones have octa-core processors, but are they better than quad-core and dual-core phones? We explain what you need to know about smartphone CPUs.

Back in the 1990s, desktop computers used to have one processor that could handle one task at a time. This is known as a single-core processor, and the way that chip companies such as Intel made them go faster was, primarily, to increase their clock speed.

It wasn’t until 2005 that the first dual-core processor was unveiled, the Pentium D. AMD followed shortly with its dual-core Athlon 64, and Intel’s Core 2 Duo was launched in 2006. See also: AMD vs Intel

Dual-core processors have two processing cores on the same physical chip and could therefore handle two tasks at the same time, increasing performance considerably.

In 2009 Intel and AMD released their first quad-core processors.

Octa-core vs quad-core vs dual-core: Smartphone processors

In smartphones we’ve seen a similar progression, with quite a few phones boasting octa-core chips. Eight cores is almost unheard of on desktop PCs, so why have phones gained extra cores so quickly?

The answer, in short, is a demand for better battery life.

Many phones use ARM processors, and while it is – relatively speaking – fairly easy to put a powerful quad-core processor in the latest phone, battery technology isn’t really up to the job of keeping that processor (along with the screen, modem, GPS and other components) fed with power all day long.

See also: Qualcomm Snapdragon 835 specs and features

So ARM developed what is effectively a dual quad-core processor: a single chip with two sets of four cores able to share the same cache memory. It calls this big.LITTLE.

Octa-core vs quad-core vs dual-core

One set of cores can deliver high performance when required (at the expense of high power drain), and the other set delivers a lower level of performance but also requires much less battery power. Usually, only one set of cores is used at one time, so for all practical purposes it’s really a quad-core processor.

The ‘low power’ cores are used for most of the time, including for tasks such as reading and sending email, navigating around the operating system, and also browsing the web. But when more power is needed, such as for intensive games or editing photos or video, the chip dynamically switches to the faster quartet of cores.

So far, the only octa-core processors we’ve seen have been in Android phones, from manufacturers including Qualcomm, Samsung, MediaTek and Huawei.

For a long time, Apple stuck with dual-core processors in the iPhone, and it was only in the iPhone 7 that it made the move to quad-core. But as with octa-core processors, the A10 Fusion chip actually uses a pair of dual-core chips, one high-performance pair and one energy efficient pair.

The big.LITTLE approach doesn't always mean there are equal numbers of high- and low-performance cores. Some phones have hexa-core processors, which typically employ a pair of powerful cores, and four power-efficient cores. There are even octa-core chips which have eight low-power cores, such as the Qualcomm Snapdragon 625.

Octa-core vs quad-core vs dual-core: Performance

Compare benchmarks, as you can in our smartphone charts, and you’ll see that an octa-core processor is not twice as fast as a quad-core. And given what you now know about the design of the chips, you wouldn’t expect them to be.

It’s the same with the iPhone 7: it’s not twice as quick as the iPhone 6s. The fact it’s 40 percent or so quicker is impressive, but that’s mainly down to the improvements made in the high-performance pair of cores, not because there are twice as many of them.

What’s particularly impressive is the way that iPhones have beaten or matched the best Android phones with – often – half as many cores.

Don’t forget that the main processor isn’t responsible for graphics performance. To a large extent this is down to the GPU – graphics processing unit. This is the biggest factor in determining how well games run on a phone, but the screen resolution must also be taken into account. You can see in this diagram that the CPU is only one of many components on a modern smartphone processor, which is called a SoC: System-on-a-chip.

Octa-core vs quad-core vs dual-core

The main point here is that a phone with an octa-core processor isn’t necessarily going to be a better choice for playing games. It may not even be a better choice for CPU-intensive apps, and this is why it’s important to read reviews and look at benchmark results if this kind of performance is important to you when choosing a phone.

Of course, we’re talking about processors and performance at a very high level here. Overall performance includes many more factors such as the size and speed of the on-board cache, the amount and type of RAM and the software being used. The latter is especially important, since apps need to be written to use all the available processing cores. This is all beyond the scope of this article, however. Suffice to say that Android – and iOS – are optimised for multi-core processors as are modern apps.

Octa-core vs quad-core vs dual-core: which is best?

So let’s get to the main question. Is it best to buy a phone with the most cores you can get? Not necessarily.

We have tested the performance of many, many phones, and there is no evidence that more cores equals better performance. As we said above, the extra cores are often there for efficiency and simply knowing the number of cores tells you nothing about the architecture of the CPU and how many of those cores are high performance.

And it doesn't really make sense to buy a phone based on its core count, just as you wouldn't buy a car purely because of the number of cylinders in its engine: there's far, far more to it.

So if you are looking for a phone upgrade, be sure to check our round-up of the best phones to buy.