Rise of the mobile processors

Mobile chip performance is accelerating at such an incredible rate that it may soon invade our desktops, as Stuart Andrews discovers

AMD versus Intel. Athlon versus Pentium. Radeon versus GeForce. For years we’ve tracked the ongoing battles between the giants of processing and graphics. Now, however, something strange is happening, something that could leave the latest developments in desktop CPUs and GPUs looking like a sideshow.

What if the real battle for the future of computing isn’t between Intel and AMD, but Intel and ARM? What if the next crucial step in graphics technology comes not from Nvidia, but from Imagination Technologies or Qualcomm? What if mobile processor technology is the mainstream?

Ever since the rise of the smartphone and then the tablet, the mobile and desktop computing paths have been converging. The PC isn’t dead – Gartner still put global sales at 87.5 million units in the second quarter of 2012 – but smartphone sales were 154 million in the same quarter, and tablet sales are set to grow to 369 million a year by the end of 2016.

What’s more, we’re seeing an explosion of mobile processing power, with the potential to transform computing. We’re not merely talking mobile CPUs and GPUs that reach desktop levels of power, but mobile architectures that might invade the desktop.

Rise of the mobile processors

The state of play

Just as the desktop processor market belongs to Intel, so the mobile processor market is dominated by ARM. The British firm designs and licenses its microprocessor architectures to others rather than manufacturing chips itself, and the list of partners making system-on-a-chip (SoC) products includes Samsung, Apple, Nvidia, Texas Instruments and Broadcom. Qualcomm licenses the ARMv7 instruction set but uses its own architecture in its Snapdragon SoC line, while Intel has its own Medfield SoC for smartphones and Clover Trail SoC for tablets, both based on the Atom architecture.

However, the CPU is only one part of the SoC picture: since it’s effectively a computer, it also needs to incorporate a memory subsystem, an I/O subsystem and a GPU. Not surprisingly, that last item has become the focus of intense competition, with ARM licensing its Mali GPU cores, Qualcomm designing its own Adreno GPUs, and Nvidia showcasing its expertise with its Tegra SoCs. Meanwhile, the UK’s Imagination Technologies has reversed the fortunes of its PowerVR technology, taking it from desktop failure to the GPU that powers the iPhone and iPad.

A few years ago, the idea of comparing SoCs with desktop processors would have seemed laughable, but not anymore. Of course, direct comparisons are difficult. As Laurence Bryant, director of mobile solutions for ARM, puts it, “it’s always hard to draw a direct parallel, because ARM processors are working in the sub-watt category, whereas your desktop processor may be 40W or more in terms of power consumption.”

A few years ago, the idea of comparing SoCs with desktop processors would have seemed laughable, but not anymore

Nvidia’s technical marketing director Nick Stam also sounds a note of realism. “They’re not as powerful as today’s Sandy Bridge or Ivy Bridge, and that difference is going to be maintained well into the future because of, basically, power.” However, the gap is closing. “I would say today that the Tegra 3 SoC performs close to a mainstream CPU that’s, say, maybe three years old. I know there are certain tests where we’re similar to a low-end Core 2 Duo.”

In terms of simple instructions per second, ARM’s next quad-core Cortex-A15 processor isn’t far behind a six-year-old Core 2 Extreme QX6700, at 35,000 Dhrystone MIPs (millions of instructions per second) against 49,161 Dhrystone MIPS. That’s a lot of performance in a low-power SoC. Meanwhile, Intel’s Clover Trail SoC looks set to banish the bad memories of the old netbook Atoms, with reports of more-than-acceptable performance in Windows 8.

It’s a similar story when it comes to graphics. Nvidia’s Stam says Tegra 3 is “not as powerful as the chip in a PlayStation 3 today, but give us another generation or two and I would say that, both from the CPU and GPU side, the SoC would be comparable to a circa-2006 PlayStation 3 in pure processing FLOPS [floating point operations per second].”

This isn’t inconceivable. Imagination Technologies claims its next-generation SGX Series6 GPUs will push more pixels per second than a mainstream GeForce 7600 GT graphics card of that same era, with a 5-gigapixel fill rate as opposed to 4.48. What’s more, Imagination claims that its tile-based deferred rendering technology makes that 5-gigapixel fill rate look like 13 gigapixels on the screen, which would put the SGX Series6 GPU ahead of a GeForce 9600 GT GPU of two years later.

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