System-on-chip technology comes of age

The silicon transistor continues to be at the heart of post-PC era products like the smartphone and the tablet. The success metrics for the transistor, however, are quite different for these mobile consumer products than they have been in the past. Frequency (clock-speed) was the primary metric in the PC era and the central processing unit (CPU) was the primary chip that drove advancements in semiconductor technology for decades. Form-factor was hardly an influencer and there wasn’t as much of a drive to integrate system-level functionality either on-chip (SoC) or in-package (SiP).

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Form-factor, cost and power for a given function are now critical drivers in the mobile market and that in turn has increased the importance of on-chip integration of functional hardware (e.g. power management, computing, audio/video, graphics, GPS and radio). This shift from mostly performance-centric chips to mostly power-constrained chips and the focus on lowering cost and increasing system-level integration is poised to disrupt the traditional semiconductor landscape. SoC technology has been used by fabless vendors and foundries for well over a decade. But it is the rapid proliferation of mobile post-PC products that is proving to be the catalyst for this technology to finally realize its full disruptive potential. Within the last five years, SoC technology has moved from being at the heart of smartphones to enabling tablets and full feature mobile computers like ultrabooks. This article describes the emerging importance of the SoC, its likely technological evolution and its potential impact on the semiconductor industry in a mobility driven age.

A post-PC world

With the advent of smartphones and tablets, the computing paradigm has begun to shift in such a way that the overall user experience is becoming a critical benchmark independent of the raw performance of the underlying technology. The Apple iPhone and iPad are great examples of this paradigm shift. Both devices provide a highly satisfactory user experience – not because they offer the fastest computing speed with the most advanced silicon but because they enable rich features at reasonable computing speed and reasonable price points.

The features of these devices collectively enhance the user experience – outstanding graphics rendering, wireless connectivity, instant-on, connected stand-by, long battery life and touch-screen apps. They may not offer the fastest raw computer performance, but they are perceived by the average consumer to be fast and provide a far superior user experience. The iPad represents the first of a wide array of post-PC products. Innovations like the Transformer (Asus), Surface (Microsoft), Nexus (Google), MacBook Air (Apple) and Ultrabook (Intel) are also aimed at redefining computing for the mobile age.

The key to the success of early post-PC products like the iPad is the fact that they were designed from the ground-up without the baggage of legacy PC-era software or hardware. Innovation around the sustaining silicon hardware technology would have called for higher performance standalone processors (CPUs) utilizing the abundance of logic transistors and even more complex layers of software to utilize the abundance of memory capacity. Instead, the new products utilize highly power constrained hardware and very lean software for accomplishing specific tasks (e.g. a video decoder to drive the display). In order to make power efficient systems for the mobile world, it is critical to shift as much of the burden on hardware while utilizing lean software. Simply force-fitting legacy PC hardware and software into a new form factor will not be as power efficient and hence will not lead to a superior user experience.

The emergence of tablets and smartphones does not herald the end of the traditional PC as we have come to know it. The PC will continue to find a place on every desk for the foreseeable future and banks of servers will continue to be used in data centers for compute-intensive applications. Yet, if history were a guide, it would suggest that the sustaining CPU semiconductor technology underlying traditional PC products is likely to be eventually displaced or at least substantially altered by the disruptive SoC technology underlying the smartphone. The rapid evolution of SoC based technology over the last few years supports this hypothesis.

Evolution – a look back

Since the advent of independent foundries at the end of the 1980s and early 1990s, the semiconductor industry has been segmented into three major entities – Integrated Device Manufacturers (e.g. Intel, AMD (pre-2009) and Samsung), fabless companies (e.g. Apple, Qualcomm, Broadcom, NVIDIA) and foundries which make chips for the fabless companies (e.g. TSMC, UMC, Samsung, GlobalFoundries).

Historically, Intel and AMD focused on making CPU-based chips (e.g. Core and Athlon) while Nvidia focused on making standalone graphics chips (GPU) for the PC and server markets. All the other players in this landscape have utilized some form of on-chip system integration (SoC) to meet the diverse needs of their respective markets.

The generic definition of a SoC is the on-chip integration of a variety of functional hardware blocks to suit a specific product application. A SoC can thus be as simple as a basic connectivity chip which combines some mixed-signal and digital circuitry. A more complex SoC may include the on-chip integration of an application processor unit (APU) and a graphics processor unit (GPU). Even more functional SoCs further integrate various other hardware blocks (e.g. image processor, audio/video decoder and modem). It is this ability to continue to integrate disparate functionality on a chip that has enabled SoC technology to rapidly evolve from supporting a simple feature-phone to a smartphone and all the way to a tablet computer.

Qualcomm started out by designing chips for the growing connectivity market with the advent of cellular telephony and the internet. Nvidia came to light as a maker of standalone graphics chips. Over time, each of these companies responded to an evolving technology trend and built upon their initial successes as they incorporated ever higher levels of functional integration into their chips. As a result, Qualcomm evolved its product line-up from standalone connectivity chips by adding an applications processor (Krait via ARM license), a GPU (Adreno via AMD Imageon buyout) and a power management unit. Qualcomm’s flagship products (Snapdragon family) now include all these blocks making it a highly functional mobile SoC product.

Similarly, Nvidia evolved from a maker of standalone graphics chips by adding an applications core (via ARM license) and a connectivity block (via Icera acquisition). Nvidia now offers highly integrated mobile SoCs (Tegra family) which power multiple tablet computers. Just a few years ago, Apple which was not even in the mobile chip design business started designing its own SoC based chips (A- family) using an application processor (via ARM license) and a graphics processor (via license from Imagination Technologies). Similarly, Samsung has also acquired all the SoC building blocks and is even taking early steps to extend this trend to server chips.

An indicator of the growing influence of the SoC is the consolidation trend within the industry. Apple acquired PA-Semi, enabling it to design its own application processors. Qualcomm recently acquired Atheros to strengthen its wireless connectivity suite and Summit Technology for enhanced power management capability. Nvidia acquired Icera to strengthen its connectivity offering and Intel acquired Infineon Wireless to gain entry into the baseband connectivity market. These acquisitions point to a consolidating market in which only a few strong players have all the required functional blocks and are getting ready to fiercely compete in the growing mobile market.

The smartphone offered the first significant platform for SoC technology to demonstrate its potential and put the SoC on a collision course with the standalone CPU. The smartphone valued on-chip integration far more than a standalone desktop. Utilizing dedicated functional blocks has several advantages over general purpose processing cores – these blocks can operate at lower frequencies while delivering higher system-level performance and consuming much lower system-level power.

In addition, by moving more functionality to hardware, the SoC enables lean software which results in lower system-level power. Using dedicated cores enables the smartphone to only turn on specific blocks for specific tasks whereas a general purpose core would have to be on all the time regardless of the task being performed. A system-on-chip is thus far better suited for mobile devices compared to a standalone CPU.

Early leadership in SoC technology put the foundry ecosystem players at a significant advantage over incumbents like Intel and the technology also benefited immensely from rapid growth in smartphone shipments. Intel was unable to break into the smartphone market for the first five years (until 2012). The introduction of the iPad and the subsequent growth in the tablet market further solidified this trend.

An indicator of the disruptive potential of the SoC is the rapid rate of advancement – not only in terms of functionality and shipped volumes but also the proliferation of a robust design and software ecosystem to support it. In just five years, the SoC technology has catapulted from enabling basic computation/connectivity on a feature phone to being at the heart of all smartphones and early stage ultrabooks, capable of a wide range of functions including audio/video, gaming, communication and productivity.