Multicore Processors Deliver PerformanceBoosts For Handheld Platforms

As designers push to improve the performance of smartphones and other portable systems, they are turning more and more to multicore processors to speed the computations, handle more audio and video operations, and provide better connectivity – all while reducing the system power envelope. At this year’s International Consumer Electronics Conference (ICES), several new multicore systems-on-a-chip solutions were unveiled by Nvidia, Qualcomm, and Samsung. These solutions promise to raise the performance bar of handheld systems to new levels by allowing multiple applications to run concurrently, render 3D graphics to support the most complex gaming applications, and deliver real-time response. Let’s take a closer look at what each of the companies has done to deliver the performance needed for next-generation systems.

The highest performance solution from the trio comes from Samsung – the Exynos5 Octa leverages the big.LITTLE concept developed by ARM to craft a system-on-a-chip design that contains eight processor cores plus lots of other system logic in a high-density ball-grid-array package (see the photo). The cores are divided into two clusters – one contains four high-performance A15 ARM processors, while the other cluster consists of four power-efficient ARM Cortex A7 cores. Only one cluster of CPU cores can be active at any time, and the cluster not in use goes to sleep to reduce power consumption. When switching between clusters, there is a 30 to 50 ms switchover delay.

The A7 cores, when in use, reduce power consumption by 3.3X vs the quad A15 cluster, but still give the system enough performance to handle most of the basic housekeeping functions and many applications that don’t require the high performance of the A15 cores. Additionally, the A7 cores are much smaller than the A15 core – all four A7 cores occupy only about half the area as a single A15 cor

This high-density ball-grid array package houses Samsung’s Exynos 5 Octa processor that contains two quad-core clusters – one comprised of four Cortex A-15 high-performance cores and the other containing four low-power second-generation Cortex A7 cores.

e, so the area penalty to add the four A7 cores has minimal impact on the chip area.

Qualcomm has crafted two new multicore additions to its Snapdragon family – the Snapdragon 600 and Snapdragon 800. The top-of-the-line 800 series, fabricated on a 28-nm process, not only has Qualcomm’s latest CPU core, the Krait 400 in a quad-core configuration, but updated versions of the company’s GPU, the Adreno 330, and the Hexagon v5 DSP engine. Furthermore, a 4G LTE Cat 5 modem integrated on the chip allows Snapdragon to connect to the fastest mobile networks. The processor cores can run at clock rates of up to 2.3 GHz, each core is only active when needed, so the entire system is designed to conserve power whenever possible. Additionally, the video support includes the ability to capture and display ultra HD, which delivers four times the pixel density of the standard 1080p display. The chip also supports displays of up to 2560 by 2048 pixels as well as Miracast wireless video streaming at 1080p.

For more conservative system designs, the Snapdragon 600 embeds a quad core Krait 300 CPU cluster that runs at 1.9 GHz, a Adreno 320-series graphics processor, and support for low-power DDR3 memory. Designers also included many other enhancements that allow the chip to deliver about 40% better performance than the previous generation Snapdragon S4 Pro processor at even lower power consumption levels.

Last of trio, NVIDIA unveiled details of the Tegra 4, which integrates four ARM Cortex A15 cores plus a second-generation battery-saver core, similar to the approach used in the Tegra 3 processor. This variable symmetrical multiprocessor architecture developed by NVIDIA allows all four A15 cores to operate simultaneously or power-down when not needed, allowing the lower power battery-saver core to take over for housekeeping and non-performance-critical tasks such as music and video playback. The integrated graphics processor unit (GPU) contains 72 custom cores that help it deliver topnotch gaming performance as well as advanced media and web capabilities, including WebGL and HTML5. Lastly, the Tegra 4 ties into the company’s Icera 450 soft-modem chipset to deliver high-throughput HSPA+ communications with data rates as high as 28 Mbits/s. Additional Icera solutions, the Icera 410 and 400 are also compatible with the Tegra 4.

These multicore processors are just the tip of the proverbial iceberg with regards to the many product developments unveiled at ICES. Future columns will highlight some of the additional developments from CES.

Dave Bursky
Chip Design Magazine

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