Three-Minute Tech: Tegra 3

[In our Three-Minute Tech series, we tell you everything you really need to know about a new technology in three minutes or less.]

If you follow the world of Android tablets and phones, you may have heard a lot about Tegra 3 over the last year. Nvidia's chip currently powers many of the top Android tablets, and should be found in a few Android smartphones by the end of the year. It may even form the foundation of several upcoming Windows 8 tablets and possibly future phones running Windows Phone 8. So what is the Tegra 3 chip, and why should you care whether or not your phone or tablet is powered by one?

Nvidia's system-on-chip

Tegra is the brand for Nvidia's line of system-on-chip (SoC) products for phones, tablets, media players, automobiles, and so on. What's a system-on-chip? Essentially, it's a single chip that combines all the major functions needed for a complete computing system: CPU cores, graphics, media encoding and decoding, input-output, and even cellular or Wi-Fi communcations and radios. The Tegra series competes with chips like Qualcomm's Snapdragon, Texas Instruments' OMAP, and Samsung's Exynos.

The first Tegra chip was a flop. It was used in very few products, notably the ill-fated Zune HD and Kin smartphones from Microsoft. Tegra 2, an improved dual-core processor, was far more successful but still never featured in enough devices to become a runaway hit.

Tegra 3 has been quite the success so far. It is found in a number of popular Android tablets like the Eee Pad Transformer Prime, and is starting to find its way into high-end phones like the global version of the HTC One X (the North American version uses a dual-core Snapdragon S4 instead, as Tegra 3 had not been qualified to work with LTE modems yet). Expect to see it in more Android phones and tablets internationally this fall.

4 + 1 cores

Tegra 3 is based on the ARM processor design and architecture, as are most phone and tablet chips today. There are many competing ARM-based SoCs, but Tegra 3 was one of the first to include four processor cores. There are now other quad-core SoCs from Texas Instruments and Samsung, but Nvidia's has a unique defining feature: a fifth low-power core.

All five of the processor cores are based on the ARM Cortex-A9 design, but the fifth core is made using a special low-power process that sips battery at low speeds, but doesn't scale up to high speeds very well. It is limited to only 500MHz, while the other cores run up to 1.4GHz (or 1.5GHz in single-core mode).

When your phone or tablet is in sleep mode, or you're just performing very simple operations or using very basic apps, like the music player, Tegra 3 shuts down its four high-power cores and uses only the low-power core. It's hard to say if this makes it far more efficient than other ARM SoCs, but battery life on some Tegra 3 tablets has been quite good.

Tegra 3 under a microscope. You can see the five CPU cores in the center.

Good, not great, graphics

Nvidia's heritage is in graphics processors. The company's claim to fame has been its GPUs for traditional laptops, desktops, and servers. You might expect Tegra 3 to have the best graphics processing power of any tablet or phone chip, but that doesn't appear to be the case. Direct graphics comparisons can be difficult, but there's a good case to be made that the A5X processor in the new iPad has a far more powerful graphics processor. Still, Tegra 3 has plenty of graphics power, and Nvidia works closely with game developers to help them optimize their software for the platform. Tegra 3 supports high-res display output (up to 2560 x 1600) and improved video decoding capabilities compared to earlier Tegra chips.

Do you need one?

The million-dollar question is: Does the Tegra 3 chip provide a truly better experience than other SoCs? Do you need four cores, or even "4 + 1"? The answer is no. Most smartphone and tablet apps don't make great use of multiple CPU cores, and making each core faster can often do more for the user experience than adding more cores. That said, you shouldn't avoid a product because it has a Tegra 3 chip, either. Its performance and battery life appear to be quite competitive in today's tablet and phone market. Increasingly, the overall quality of a product is determined by its design, size, weight, display quality, camera quality, and other features more than mere processor performance. Consider PCWorld's review of the North American HTC One X; with the dual-core Snapdragon S4 instead of Tegra 3, performance was still very impressive.

For comprehensive coverage of the Android ecosystem, visit Greenbot.com.

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