Evaluating Tablet PCs Based on Processors

A tablet's processor can offer clues about speed and function

Nvidia Tegra 4 processor

Nvidia Corporation

When purchasing a tablet device, most people don't think about processing power. However, the type and speed of a processor could make a huge difference in the overall functionality of a tablet. Because of this, buyers should be aware of typical processors and what to consider when purchasing a tablet.

The majority of the processors used in tablets right now are 32-bit, but more products with 64-bit processing are emerging. This has big implications when you compare both performance and clock speeds.

ARM Processors

Most tablets use a processor architecture produced by ARM. This company designs the basic processor architecture and then licenses those designs out to other companies to manufacture. As a result, there are similar ARM-based processors manufactured by a wide range of companies.

The most dominant ARM processor design for tablets is based on the Cortex-A. Below is a list of the nine Cortex-A models and their features.

Cortex-A5 Lowest power consumption. Generally single-core. Frequencies between 300 and 800MHz.
Cortex-A8 Modest processor with better media performance than A5. Generally single or dual-core. Frequencies between 600MHz and 1.5GHz.
Cortex-A9 Most popular of the processors. Typically dual-core but available with up to four. Frequencies between 800MHz and 2GHz.
Cortex-A12  Similar to the A9 but with wider bus paths and improved caching. Available with up to four cores. Clock speeds up to 2GHz.
Cortex-A15 32-bit design. Typically dual or quad-core. Frequencies between 1GHz and 2GHz.
Cortex-A17  Newer more efficient 32-bit design similar to the A15 but with slightly better performance. Up to 4 processor cores. Clock speeds between 1.5GHz and over 2GHz.
Cortex-A53 The first of the new 64-bit processors. Has between one and four cores.  
Cortex-A57 Higher power 64-bit processor intended for consumer electronics and computers more than tablets. Has between one and four processors.  
Cortex-A72 Latest 64-bit processor, intended for consumer electronics or PCs rather than tablets.    

These designs are considered systems-on-a-chip (SoCs) because they also integrate the RAM and graphics into a single silicon chip. This has some implications, as two similar chips' processor cores may have different amounts of memory and different graphics engines, varying the performance.

Manufacturers might alter the design slightly, but for the most part, performance will be very similar between products within the same base design. The actual speeds can differ, though, because of the amount of memory, the platform's operating system, and the graphics processor. However, if one processor is based on the Cortex-A8 while another is based on Cortex-A9, the higher model will typically offer better performance at similar speeds.

In 2011 Microsoft released Windows 8 RT specifically to run on ARM processors, but due to its limitations, the mobile OS was discontinued. You'll deal with Windows 8 RT only if you're working with an old or refurbished tablet.

x86 Processors

The primary market for x86-based processors is a tablet PC that runs the Windows operating system, primarily because existing versions of Windows are written for this type of architecture. The two major suppliers of x86 processors are AMD and Intel.

Intel's Processors

Intel is the most frequently used of the two, thanks to its low-power Atom processors. They may not be as powerful as traditional laptop processors, but they still provide sufficient performance for running Windows, albeit somewhat slower. Intel offers a wide range of Atom processors, but the most common series used for tablets is the Z series because of its lower power consumption and reduced heat generation. But these processors typically have lower clock speeds than traditional processors, which limits their potential performance.

A newer X series of Atom processors was released that offers greatly improved performance over the past Z series with just as long or longer battery life. If you are looking at a Windows-based tablet with an Atom processor, it is best to look for one with a newer x5 or x7 processor, but if it uses the older processor line, try to get the Z5300 or higher.

Serious business-class tablets that use energy-efficient Core i series processors are on the market. They offer a similar level of performance but generally are not as compact or have the same level of running times as the Atom-based processors.

The Core M series of processors also offer performance somewhere between the Core i5 and the Atom processors. They are well suited for tablets, as some models don't require active cooling.

Intel rebranded newer versions of Core i series processors with 5Y and 7Y model numbers.

AMD's Processors

AMD offers several processors that could be used in tablet PCs, as well. These are based on AMD's APU architecture, which is just another name for a processor with integrated graphics. There are two versions of the APU that could be used for tablets. The E series was the original design meant for low power consumption; it's been on the market and refined over time.

The more recent offerings are the A4-1000 series, which are ultra-low wattage and can be used with a tablet or 2-in-1 hybrid laptops.

The faster the performance of the x86 processor, the more power it will typically consume and the larger the tablet will have to be to properly cool the processor. It will likely have a shorter battery life due to increased power consumption. Prices will also be more expensive the more powerful the processor is.

Why Number of Cores May Matter

Most software now is written to take advantage of multiple core ​processors. This is referred to as multi-threaded software. The operating systems and software can allocate tasks to be run in parallel between two different cores within a processor to help speed up the performance. As a result, a multiple-core processor is generally preferable to a single-core processor.

Multiple cores are great for multitasking, as well, for example, using a tablet to listen to music while surfing the web or reading an e-book. With two processors, a tablet can better handle multiple tasks by assigning each to an individual processor core, rather than having to swap processes between a single core.

But having too many cores can increase the size and power consumption of a tablet PC. While it's possible to have up to eight cores, most tablet software has a limited set of capabilities that won't benefit much from more than two cores. This may change in the future, however, as tablets become more widespread and their uses evolve.