By: Dr Finbarr Moynihan, General Manager – Corporate Sales International, MediaTek Inc.
With the rapid growth of innovation in smartphone and tablet markets, there is a corresponding increase in the variety and capabilities of mobile processors that aim to deliver high-performance computing, communications, graphics and multimedia functions – all while respecting the power budget and battery life constraints of today’s mobile devices.
A typical mobile application processor integrates a computing unit (CPU), a graphics unit (GPU), multimedia and communications (Connectivity) functionalities. All these elements hold immense potential for technological innovation, both as a combined unit and in their individual capacities.
1. Mobile Computing
As mobile processors run more powerful operating systems, such as Android, Windows and even Chrome in the future, there is an increasing need for more computing power. Much like the trend in the past in the PC industry, the initial increase in computing capability was achieved with a combination of CPU architectural enhancements and frequency scaling to increase performance.
In today’s leading semiconductor process technology – like 28nm – it is possible to operate some of the CPU cores in the 2.0–2.5GHz range – which is about the maximum frequency that any one CPU core can operate. Beyond scaling performance with increasing operating frequency, modern mobile processors have adopted both multi-core architectures and newer heterogeneous multi-processing
(HMP) architectures, based on ARM’s big.
LITTLE concept to further improve performance. For instance, MediaTek’s MT6592 mobile processor was the first to integrate 8 Cortex-A7 CPUs in a true Octa-core configuration – each capable of operation up to 2GHz. Based on hardware (HW) and software (SW) extensions to the standard ARM multi-core CPU configuration and SW scheduler algorithms, the MT6592 allows for operation of any combination of the CPUs (from 1 to 8).
As modern mobile SW, for instance advanced browsers like the Chromium browser, gaming applications and multimedia codecs, are written more and more to take advantage of scalable multi-core, multi-threaded architectures, the MT6592 can turn on more and more of the CPUs – when increased performance is needed. The cores do not run all the time, and often for basic OS tasks, it may be only one or two cores that are operating, with the others gated off. This allows for high peak performance when needed, but low power consumption when the performance is not needed.
The next step in scaling the performance of mobile processors is the use of HMP & the big. LITTLE architecture. In these architectures, the mobile processor includes two clusters of CPUs – with a different CPU being used in each cluster. For instance, the MediaTek MT6595 mobile LTE processor integrates a 4+4 configuration consisting of a cluster of 4 big cores (Cortex A-17) and a cluster of 4 LITTLE cores (Cortex A-7).
The MT6595 operates the big cores at up to 2.2GHz and the LITTLE cores at up to 1.7GHz. The basic tradeoff here is that Cortex A-17 big cores offer significantly more peak performance per core (higher single-core/single-thread) computing performance that can be harnessed (either a single-core or multi-core configuration to give extremely high computing performance when needed for tasks, like browsing, that need this performance.
The disadvantage is that the power consumption is much higher. For less demanding tasks the cluster of LITTLE cores can be used. Actually, taking advantage of MediaTek’s innovative CorePilotTM technology for HW and SW scheduling, the MT6595 can operate with any combination of big and LITTLE cores to match the performance/power for the task required.
As we look to the future trend in CPUs for mobile processors, we are just about to enter the world of 64-bit CPUs that are enabled with the new ARM v8 cores. These new CPU cores will bring the full capability of 64-bit processing to the mobile space. We will see the adoption of both big and LITTLE cores in this new 64-bit family.
The introduction of 64-bit CPUs will further increase the per-core computing performance, and allow for applications to use increased memory and for closer compatibility between mobile and desktop computing platforms. Future versions of the Android operating system are expected to offer support for 64-bit cores. In a matter of few years, smartphones should be more powerful than today’s desktops and more robust processors packing sub-20nm, 64-bit may become a reality.
Higher-end mobile processors today are offering support for the newer LP-DDR3 memory with dual-channel (2x32bit buses) support at frequencies up to 933MHz. Future premium mobile processors are planned with support for more advanced LP-DDR4, in some configurations up to 128-bit buses (4×32-bit) and speeds up to 1600MHz.
2. Mobile Graphics
Along with the growing need for more performance, larger screen sizes and better resolutions in mobile devices like smartphones and tablets, there has also been an increasing demand for higher GPU performance. Mobile GPU performance has been steadily increasing through the adoption of new GPU core architectures – such as the new Imagination PowerVR Rogue family or the ARM Mali T-6xx and T-7xx cores. It can further be increased by using higher clock frequencies, more advanced process technologies and multi-core configurations.
Further extending the capabilities of the HMP concept, some modern mobile processors are also taking advantage of the GPU hardware to run computational tasks. With many modern mobile processors, the silicon area dedicated for the GPU is often larger than the area dedicated for the CPU and it can sometimes be more power efficient to run computational tasks on the GPU core – for instance this
might make sense in advanced imaging algorithms and computational photography.
New software APIs, such as OpenCL from the Khronos group, Renderscript for Android and DirectCompute from Microsoft, are all designed to allow for running of computational tasks on the GPU hardware. This trend is expected to continue, as the need for higher performance while maximizing power optimization drives the mobile processors market.
2. Display, Video, Imaging & Multimedia
In the past many of the multi-media functions like camera interface, display, video encoding and decoding, and audio processing needed on mobile devices were managed by dedicated co-processors. The idea behind co-processors is to perform extremely specific, dedicated functions, and they’re all meant to keep the main SoC from turning on and burning through a bunch of power.
Nowadays, these functions are often integrated into the mobile processor as well, creating a typical mobile SoC processor that handles all the multimedia functions for the mobile device – as well as the computational, communications and graphical functions.
A modern mobile processor should be capable of supporting a 50-megapixel sensor and the processing needed to stitch images together, to create panoramas and to apply a host of effects and filters. In future, the biggest feature requirement of mobile processors would be the support for ultra-high definition (UHD), enabling users to stream and create 4K UHD content, take HD clips and upscale them.
Smart devices, powered by ultra-modern processors are going to usher in the age of ultra-high definition because UHD technology is bound to spread faster though smart devices than TVs, as people upgrade their phones more frequently than their TVs. Audio processing including super high-end 110dB SNR audio is expected to dominate the smartphone space in near future, which would enable DTV quality audio output for music and video playback.
4. Mobile Connectivity
Today’s leading mobile processors integrate the cellular baseband, covering support for 4G LTE and 3G HSPA+ connectivity allowing for mobile broadband connectivity on mobile networks worldwide. It is common now to have support for 3G data rates up to 42 Mbps and G/LTE Category 4 up to 150Mbps.
In future, mobile processors will integrate support for the so-called LTE-Advanced standards that will support the so-called Carrier Aggregation feature that will enable peak data rates of 300-450Mbps. Also, as of now most modern mobile processors integrate support for local connectivity like Bluetooth, GPS and WiFi – today the chipsets either offer integrated support for Wi-Fi standards like 802.11n or support the newer 802.11ac standard (offering higher data rates) via external complimentary combo chips. But going forward, we can expect that the digital baseband support for 802.11ac will also be integrated into the mobile processors.
Additionally, mobile processors are aiming to deliver some futuristic features like wearable sensors, biometric identification and indoor positioning (IPS). In another decade, we could be sporting wearable sensors imbedded in belts, spectacles, shoes and other apparels, besides just watches, which would aim to monitor our health conditions and provide preventive, precautionary and curative actions.
Biometric identification through smartphones is already a reality. Further technological innovations will enable mobile processors to deliver this through voice, retina and fingerprint sensors. IPS installations in future mobile processors will provide indoor positioning of a device/ person, making use of technologies like RTLS (real-time locating system).