Guide to smartphone hardware (1/7): Processors

With such a huge range of smartphone hardware on the market today from vendors such as Samsung, HTC, Apple, Motorola, LG and more, it can be very confusing to keep up with what exactly is inside each of these devices. There are at least 10 different CPUs inside smartphones, many different GPUs, a seemingly endless combination of display hardware and a huge variety of other bits and bobs.

This multi-part guide is intended to help you understand each and every one of the critical components in your smartphone and how they compare to other hardware on the market. Each section is intended to give you all the necessary information about the hardware, and even more for the tech enthusiasts out there, so expect them all to be lengthy and filled with details.

Over the next several days and weeks we’ll be posting up another part of the guide. In today’s guide I’ll be looking at smartphone processors: the different brands, types, how they perform and the critical differences between them.

System-on-a-Chip

This is a term you’ve probably come across before, and for good reason. When reviewers are talking about the processors inside a smartphone they are usually actually referring to the system-on-a-chip: a combination chipset that features things such as the actual processor cores, the graphics chipset, the RAM and possibly ROM as well, interface controllers for things such as USB and wireless tech, voltage regulators and more.

The idea behind a system-on-a-chip, or SoC, is that all the critical components of a device are located in a relatively small area on the device. This reduces the size of the component board needed inside and also can help make the device itself faster and more battery efficient. They also help reduce costs for assembling the product and can also be cheaper than an equivalent multi-chip set-up.

I’m more specifically looking at the processing cores inside the SoC as well as available SoC packages today, but you can look out for the other parts of this article for more detailed information on the graphics chip, memory and more.

What does ARM have to do with it?

References to ARM when it comes to SoCs can unfortunately be confusing. ARM is essentially three things: a company, a microprocessor architecture and processor core; all of which you may have guessed are related. ARM Holdings plc is the British-based company that, since 1983, has developed the ARM microprocessor instruction architecture which is used inside their ARM processor cores.

Where other companies like NVIDIA, Texas Instruments and Samsung come in is in the production of the SoCs. They take (through licensing) the ARM developed and produced processor core and put it inside their chipsets in combination with whatever GPUs, memory and other things they desire. Qualcomm is a slightly different story, but we’ll get to that later.

This is why two SoCs from different companies can both appear to contain the same processor, such as how both the TI OMAP3630 and Samsung Exynos 3310 use a single-core 1 GHz ARM Cortex-A8 solution. They are different though in their use of other components, such as how the OMAP uses a PowerVR SGX530 GPU but the Exynos features the SGX540.

The ARM1 building in Cambridge, where integral parts of smartphones are developed

The ARM architecture is something that you don’t really have to worry about when looking at a new smartphone as almost all new ARM processors feature their ARMv7 architecture. The older ARMv6 architecture was used on old ARM11 processors, which in turn were used in old SoCs on devices such as the HTC Dream (T-Mobile G1, the first Android phone) and iPhone 3G.

Currently there are two ARM processor types that are widely in use: the ARM Cortex-A8 and ARM Cortex-A9 MPCore; both use the ARMv7 architecture. Without getting extremely technical, the Cortex-A8 is usually found in single-core implementations and the Cortex-A9 in devices with up to 4 cores. The A9 is the newer implementation and as well as being (usually) multi-core, it is slightly faster per MHz than the A8 processors (2.0 DMIPS/MHz vs. 2.5 DMIPS/MHz).

You’ll find the ARM Cortex-A8 processor inside SoCs such as the TI OMAP3 series and Samsung’s SP5C series (Hummingbird/Exynos 3xxx). The Cortex-A9 is found in the TI OMAP4 series, Samsung Exynos 4xxx series, NVIDIA’s Tegra 2/3 and the Apple A5.

ARM also makes the Mali range of graphics processors, which I’ll be looking at in the graphics part of this series.

In the future we’ll be seeing SoCs that feature ARM’s Cortex-A15 MPCore, which is allegedly 40% faster than the Cortex-A9. We should see these in the TI OMAP5 series, Samsung Exynos 5xxx series and the Tegra "Wayne" series in late 2012/early 2013. In the distant future we can also expect ARM cores that use their ARMv8 architecture.

Qualcomm processors and Snapdragon SoCs

Qualcomm is slightly different to the other SoC manufacturers in that they don’t actually use the reference ARM processor core designs. Instead they take cues from the ARM Cortex-A8 and make improvements that they package into their very own Scorpion and Krait CPUs. This obviously requires more research and development than say the TI OMAP series, but is apparently slightly better for media-related operations and power efficiency compared to the standard Cortex-A8.

These processors make their way into Qualcomm’s Snapdragon range of SoCs, which are split up into different series. Each series is numbered from S1 to S4 (currently), and the higher the series the more powerful and (usually) the more recent the SoCs are. As of writing there are no products on the market that make use of Qualcomm’s S4 chipsets, but they are on their way shortly.

Snapdragon SoCs are usually named using a three-letter designation followed by four numbers. “QSD” was used on the older S1 processors, followed later by “MSM” for devices with wireless connectivity and “APQ” for those without. When it comes to the numbers, the first (eg. 8xxx) indicates the class with 7 usually meaning low range and 8 meaning mid/high end. The second number (eg. x2xx) indicates whether the device is GSM or CDMA, with 2 indicating GSM and 6 indicating CDMA. The final two numbers usually designate the performance grade of the CPU: eg. the MSM8255 is a 1 GHz S2 single-core, then up to the MSM8260 1.2 GHz S3 dual-core, and then to the future MSM8270 Krait-powered S4 Snapdragon.

Both S1 and S2 Snapdragon SoCs are single-core only, ranging up to 1.5 GHz via their Scorpion processors inside. S1 was the primary and only processor type allowed in the first batch of Windows Phones, using the 1 GHz QSD8x50, and was also used in some Android devices such as the HTC Desire, HTC Droid Incredible, Nexus One and HTC EVO 4G.

The S2 Snapdragons are used in a much wider range of products. S2 differs from S1 in that there is a more powerful graphics processor inside along with a decrease in process from 65nm to 45nm, which helps conserve power and heat output allowing for larger CPU clocks. You’ll see the 1 GHz MSM8x55 in a huge range of Android products such as the HTC Desire HD, HTC Desire S, HTC Thunderbolt and pretty much all of Sony Ericsson’s first-batch of Xperia devices (including the Xperia Play).

There is also a faster S2 SoC which is the MSM8x55T which is clocked between 1.4 and 1.5 GHz. This is seen in a lot of the second generation Windows Phones such as the Nokia Lumia series, HTC Titan and Samsung Focus S. It is also used in a few Android devices such as the HTC Flyer and Samsung Galaxy W.

The S3 Snapdragons see a jump from single-core to dual-core SoCs, as well as a graphics boost. These devices are manufactured using the 45nm process and the Scorpion cores used are still Cortex-A8-based, as opposed to other dual-core SoCs that use newer Cortex-A9 technology. You’ll find the 1.2-1.5 GHz S3 MSM8x60 in products like the HTC Sensation, HTC EVO 3D, HTC Rezound and some Samsung Galaxy S II models.

Apart from the obvious differences in each series’ processor and graphics chips, along with progressively smaller manufacturing processes, each series improves on other capabilities such as camera resolution, screen resolution and media tasks. Below is a quick rundown of each series in these respects.

  • Snapdragon S1: Supports up to 720p displays, 720p playback and 720p video recording. Supports up to 12 megapixel cameras. Supports up to HSPA radios
  • Snapdragon S2: Improves on S2 by adding support for HSPA+. Better graphics hardware
  • Snapdragon S3: Supports WSXGA (1440x900) displays, 1080p playback and 1080p recording. Supports full stereoscopic 3D capabilities including dual-cameras, recording and playback. Supports up to 16 MP cameras. Adds Dolby 5.1 surround sound support and echo/noise cancellation

Of course devices that choose to use a certain Snapdragon SoC may not choose to fully utilize the maximum capabilities of the chipset, and in fact most don’t.

A chip block diagram for the Snapdragon S4 SoCs using Krait CPUs

The next step for the Snapdragon line is the S4 series, which ditches the Scorpion CPU in favour for Qualcomm’s new Krait CPU. Krait allows for up to four cores in the SoC at up to 2.5 GHz per core, and is made on their new 28nm process. S4 also improves greatly on the GPU inside and memory capabilities, includes LTE support in the SoC, 1080p display and HDMI support, up to three 20 MP cameras, up to four microphones for recording/noise cancellation, Dolby 7.1 surround sound support, dual-band WiFi support and Bluetooh 4.0 capabilities. Qualcomm also claims that the CPU is less power hungry, which I’m guessing is mostly down to the decrease in manufacturing process size.

We should be seeing new devices with the Snapdragon S4 chipsets inside sometime this year, first announced in the Lenovo IdeaTab S2 10-inch tablet. The IdeaTab S2 should have a 1.5 GHz dual-core S4 Snapdragon 8x60A inside.

Until then, a good idea of how Qualcomm’s top-end Snapdragon S3 SoC performs can be seen in our HTC Sensation review, and from personal experience with the device it performs very well. I eagerly await testing a device with Krait inside though to see how it matches up not only to the older Snapdragons but to other SoC offerings.

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