Guide to smartphone hardware (1/7): Processors

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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