Android device performance drivers: Intelligent design or number of cores?

Telecom Lead Asia: Michael Civiello, senior director of marketing for Broadcom’s Mobile Platforms Business Group, says intelligent design — and not the number of cores — improves Android device performance.

Multicore implementations are ideal for certain requirements, yet the value of mobile multicore performance may not be as simple as determining the sum of its parts. All cores must still share the balance of resources in a device, such as battery and memory, so doubling or quadrupling the number of cores does not equal twice or four times the performance. Given the pace of advancements and the commonly diverse use of smartphones and portable devices today – gaming, multimedia viewing, social media, email and so forth – I would argue that smarter chip implementations and architectures are a far more important factor.

The number of cores in the central processing unit (CPU), coupled with CPU frequency (GHz), is often touted as the most important set of parameters in the specification of a mobile platform. Yet more sophisticated core structures – purpose-built for mobile considerations, and incorporating low power hardware accelerators – are proving capable in delivering higher performance, lower power solutions ideal for mainstream Android users.

Myth #1: More Cores Mean Better Performance

Because raw applications processing has become a mainstay requirement for manufacturers of mobile devices, consumers have suffered with devices that routinely have higher power consumption, poor battery life, and reduced graphics capabilities. Android, on the other hand, has begun migrating its architecture to offload tasks from the CPU to the graphics processing unit (GPU) and other hardware accelerators. This offload strategy saves power and frees up the CPU for applications. Further, overall user experience is more closely coupled to the complete SoC design, including hardware and software, rather than just the CPU.  This general trend toward a GPU-centered architecture is driving developers to re-focus designs on Android performance.

In one scenario, a high performance GPU is essential for a satisfying on-screen gaming experience, but so is the platform’s overall thermal envelope. Since gaming generally presents a consistent load to the CPU, performance available to the system is determined by the maximum power allowance of the CPUs.  By incorporating low-power offload cores, the mobile device is able to optimize remaining power specifically for the CPU, which in turn maximizes game performance.

Myth #2: All Processors Are Created Equal

Contrasted with quad core deployments, the full spectrum of mobile device performance, image processing and power consumption is better managed with intelligent dual core solutions, developed in tandem with processors designed to offload specific tasks. Performance realities of how a mobile device is actually used are based on the broad balance of technologies embedded in the device – considering system architecture, available memory bandwidth, latency, and GPU hardware all working together for seamless high performance.

Perhaps most importantly, developers must acknowledge that all chips are not created equal in terms of sophisticated features and proven performance.  The ARM processor may act as the CPU building block used for Android-based devices, but manufacturers are keen to differentiate performance with their own modifications and innovations developed through technology expertise and highly competitive research and development.

Android relies heavily on the GPU for drawing the user interface (UI), often fully composing the UI elements. Common to all applications which require screen display, this activity is a critical factor in the overall performance and power consumption of an Android device.  As a result, power-optimized GPUs positively affect battery life across virtually all Android user scenarios.

For example, Broadcom’s new concept quad-core (2+2) architecture facilitates intelligent offload to both GPU and VPU (Vector Processing Unit) cores. Resultant power-savings enable performance up to 1080p high-definition video and support for up to 42-MP camera solutions.   Developers should anticipate growing demand for these types of creative offload methods, particularly as Android moves from one generation to the next.

Myth #3: Today’s Mobile User Demands Multicore

Both developers and end-users must recognize that employing the right processor for the right task offers greater performance value than the more common practice of simply adding more cores. In fact, multicore processing has tangible impact on a very small subset of Android user scenarios. In many cases, the second processor in a dual core system operates well below peak capacity most of the time, and the third and fourth processors of a quad core architecture are often idle.

In the new concept quad-core example, the CPUs are lightly loadedbecause much of the system’s complexity has been offloaded to the device’s customized hardware, including a high performance GPU and dual VPU. Performance improves as processing tasks are offloaded from the CPU, in turn saving power and freeing up CPU cycles that can be applied to value-add applications running on the main cores.  As a result, Broadcom’s BCM28155 Android-based device using a new concept quad-core (2+2) solution has performance headroom for an improved Android user experience.

Of course, there are some instances in which a quad core processor device can improve performance. Most of these are multimedia-heavy processes such as video editing, transcoding, facial recognition or 3D stereo games. At the same time, while they can be configured to use a quad core processor, most can also rely on solutions such as Broadcom’s new concept quad core (2+2). The dual CPU and dual VPU, quad processor architecture delivers high levels of performance, achieving excellent concurrency at very low power consumption – proven using an HD LCD and operating with 1080p encoding and decoding.

Performance Advances Demand Intelligent Core Deployments

Intelligent core usage balances performance, image processing and power consumption in Android devices. Smarter dual core solutions, deployed in tandem with processors developed to offload specific high performance tasks, enable devices to not only deliver performance comparable to that of quad core solution, but also to perform with sufficient headroom for flexible handling of new mobile tasks and applications. These are dramatic performance advantages – significant because they neither exceed power budgets nor reduce the overall device standby or talk time.

Perceived multicore value has been ingrained into the public conscious, but more is not always better. Deploying a more sophisticated and purpose-built core structure combined with low power hardware accelerators, is proving to be a smarter path for developers – enabling higher performance, lower power solutions for an improved Android user experience.

Note: As senior director of marketing for mobile platforms in the Mobile and Wireless Group at Broadcom, Mike Civiello is responsible for the global business development of complete chipset solutions for cellular phones.  He has been at Broadcom for more than eight years and in the wireless semiconductor industry for more than 25 years.

By Michael Civiello, senior director of marketing for Broadcom’s Mobile Platforms Business Group
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