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PROCESSOR CORES IN SMARTPHONE SoCs

A processor core in a smartphone is a unit inside a smartphone SoC that can be considered as the brain of the phone. In simpler terms, A core is a processing unit within an SoC.

Processor cores in smartphone SoCs is a unit inside responsible for handling data processing. It is the brain of the phone. In simpler terms, A core is a processing unit within an SoC. This unit is the most important part of a smartphone. The processing power of a phone can be determined simply by looking at the processor cores in Smartphone SoCs.


Read: What is an SoC?


If good powerful cores are used, you can use your phone to carry out heavy tasks. These include: playing high definition games, loading heavy apps, and use your phone with very little lag etc. But if your phone comes with below average or weak processor cores, you may be unable to play high definition games on your phone. Even using Facebook or Instagram will give you a headache as the phone may lag badly.

Image credits: Wikipedia Commons

All processor cores in smartphone SoCs are designed by a company called ARM holdings. ARM holdings do not make cores or produce any chips. Instead they produce designs for Mobile computing and sell them to semiconductor companies that actually manufacture these chips.

ARM cortex cores uses RISC (Reduced Instruction Set Computing). This means that they’re designed to handle less complex tasks or tend to break difficult tasks into smaller sections before attempting to process them. This is different from Intel CPUs on PCs that use CISC (Complex Instruction Set Computing) that can simply blaze through any task at a go.

They are the only company that design processor cores for smartphones.
They sell in two methods:

i. Core license

If you buy a core license from ARM, you are not allowed to tamper with the design. You will manufacture the processor core the way it was designed by ARM and either use it or sell it to the companies that produce smartphones. Examples of core licensees are Mediatek and Unisoc.

ii. Architectural license

If you buy an architecture license from ARM, you would be allowed to tamper with or customize the design to produce a processor core that meets your taste. These modified processor cores are referred to as “custom cores” and in most cases, they perform better than normal cores. Examples of custom cores are Krait and Kryo by Qualcomm Snapdragon, Mongoose by Samsung Exynos, Cyclone, Typhoon, Twist and Swift by Apple Bionic.

Every smartphone in use today uses one of these two types of cores. If you use a phone with a Snapdragon, Exynos or Bionic SoC, the processor cores inside these are customized. If you use a phone powered by Kirin, Mediatek or Unisoc, then those are normal cores.

CORE COUNT

Inside an SoC, there could be different numbers of processing cores. Around 2015, it was very common for phones to have four (quad) processor cores but in 2020, eight (octa) cores is the new standard.

Each one can handle tasks independently, or can be combined to provide more power to particularly CPU-intensive tasks. In normal use, a multi-core processor will see the cores share the workload of the OS and all your running apps without ever reaching their maximum clock speed. The result is a snappier, more responsive device, with better multitasking support, plus lower heat emissions and less power consumption.

THE big.LITTLE ARRANGEMENT

What most SoCs use today is what is called the big.LITTLE in which the CPU cores are divided into big and small cores. The smaller less powerful cores handle easy tasks like texting, chatting, watching a movie while the bigger, more powerful and faster cores handle the more difficult tasks like playing HD games (e.g. PUBG or Fortnite).

This method is used because, the cores are arranged into two distinct groups based on performance. The big cores give high performance but tend to heat up and drain a lot of battery, while the small cores are only good for small task and they save battery too. If your big cores were in use all the time, your phone would over heat and your battery may not last long i.e. your battery lasts longer when you are watching movies than when you are playing games.

ARM ARCHITECTURE AND CORES EXPLAINED

ARM cortex CPU cores come in data sizes of 32 and 64 bits as well as instruction sets of 16 bit thumb and 32 bit ARM. The larger the number, the better.

If you are buying a phone from a honest manufacturer, they’ll put the type of CPU cores in the advertisement. Some of us buying phones must have seen words like ARM cortex 53, 72, 73 etc.
Here are a list of all the ARM cortex cores made:

Instruction sets

The Cortex-A5 / A7 / A8 / A9 / A12 / A15 / A17 cores implement the ARMv7-A architecture. The Cortex-A32 / A34 / A35 / A53 / A57 / A72 / A73 cores implement the ARMv8-A architecture. The Cortex-A55 / A65 / A75 / A76 / A77 cores implement the ARMv8.2-A architecture.

The A30 tier have low performance. The A50 tier (with the exception of the A57) have mid performance and the A70 are high performance.

In the big.LITTLE arrangement, the A70 tier are used as the big cores that give high performance (which drains battery), the A50 and A30 tier are used as little cores for low performance tasks (like making calls and watching movies) which conserves battery.

Image credits: Wikipedia

CLOCK SPEED

A clock speed is the time taken for a processor core to fetch data from your phone, decode it and execute it to produce an output (fetch-decode-execute). For example, if you are chatting and you hit A on your keyboard, your processor core will fetch that instruction from the keyboard, decode it and then send the letter A to appear on your screen. The time taken to carry out the fetch-decode-execute phase is referred to as the clock speed. It is measured in Gigahertz (GHz).


Read: Instruction Set Architecture versus Clockspeed


Some people erroneously use clock speed as a yardstick for determining the performance of a processor. This is not so. You can only use clock speed to compare two SoCs, when they use the same type of cores. e.g. A53 vs A53. If you are trying to compare different SoCs using different cores, then the one with the more advanced architecture wins every time e.g. A57 vs A76 (A76 is better regardless of the clock speed of the A53).

Image credits: Android Authority

Conclusion:
All processor cores used in smartphones today (both normal and custom cores), are built off the designs of the cores listed above in the table. So next time you are getting a phone, do well to check these specs. A good phone should have at least high performance cores of A72 and above and low performance cores of A53.


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