Nvidia Tegra 2: the future of smartphone graphics

How Nvidia plans to dominate mobile graphics

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Tegra 2 is Nvidia's latest-generation mobile graphics chip, announced at CES 2010 back in January.

According to the company, it has been "designed to power the new generation of tablets, slates, smartbooks, e-readers, automotive safety and entertainment solutions, and Internet TV boxes."

Which tells you something about the recent proliferation of form-factors as well as Nvidia's ambition. It marks a strategic shift by Nvidia, away from the mobile GPU and into a full integrated 'solution'.

As an Nvidia Corporate Communications Manager admitted, "the mobile GPU never really got off the ground. It was too power hungry and nobody really knew what to do with it."

Apple's iPhone woke everybody up to the smartphone idea and now the market has nowhere to go but up – and it's predicted to double over the next three years.

At the heart of these electronic devices, which is a SoC, or System on a Chip. This little fellow is a processor, graphics, audio, controller and more in one handy slice.

Beyond Zune HD

But what happened to the original Tegra? It was launched in 2008 and Microsoft used it in the Zune HD and it found its way into a couple of other devices but, lets be honest, it didn't set heartbeats a flutter.

The green army's second stab looks much more promising. It could mean phone, HIDs, netbooks and their ilk finally get to do what we want, such as play decent video.

The basic design is as before. An ARM processor mated with Nvidia's GPU, northbridge (handles the communication between chip, RAM and BIOS), southbridge (the I/O hub) and a memory controller. It's shrunk from a 65nm process to 40nm. All that's missing is the memory and a modem, apart from that it's almost the whole machine in one.

This time around the processing power is provided by a dual core ARM7 Cortex-A9. Advanced RISC Machines used to make chips for the BBC Micro but, when squeezed out of the desktop market by the mighty x86, took to licensing its low-power designs.

You'll find ARM-based chips in iPods, graphics cards and over 90 per cent of the world's mobile phones, so you probably already own one. The Cortex-A9 architecture features (deep breath) a high efficiency, dynamic length, multi-issue superscalar, out-of-order, speculating 8-stage pipeline. Short answer: it's a corker.

The previous Tegra used an ARM11 design (dating from 2003) and was criticised for its sluggishness. Nvidia has gone for two Cortex-A9s.

There are eight basic sections to the Tegra 2 chip, alongside the two A9s, we have a HD video decoder processor, a HD video encoder processor, an audio processor, a 2D/3D graphics processor and an image processor.

The graphics sub-systems are Nvidia's territory of course, and the bit it's been trumpeting about most loudly. It's the same general architecture as the original Tegra, just faster thanks mainly to memory bandwidth, you get LPDDR2 verses LPDDR1.

As before it supports OpenGL and has programmable pixel shaders, vertex and lighting. 3D performance is claimed to be double the first generation. How fast it is has yet to be proved, there are some dubious bar charts, but given the silicon specs it has to be good.

Possible display modes include a 1,920 x 1,080 for 1080p video, WSXGA at 1,680 x 1,050 for LCDs, UXGA at 1,600 x 1200 for CRTs (for those still running glass) and NTSC/PAL output for the telly. Tablet PCs are clearly in mind here.

Accelerated web video

Support for Flash is there; as lack of it helped Microsoft's Zune get overlooked. If it can't run Facebook the kids don't want it. The Tegra 2 is the first processor to run 100 per cent accelerated Flash 10.1. The HD video decoder can deal with a full 1080p MPEG-4 stream. More importantly it can do it on its own.

One thing that previously scuppered HD video on handhelds is the high demands on the CPU, which means battery life took a battering.

The audio processor has a decent pedigree too; Nvidia bought PortalPlayer in 2007, who made the processors for the first five generations of the iPod. The image processor is there to drive a digital camera and can support up to 12MP.

Finally there's also another ARM processor on board, an ARM7. This does the housekeeping and dusting and makes sure all the other processors and talking to each other politely and have clean socks. For anything not tethered to the wall its all about getting the functions you want at the lowest possible power consumption.

Nvidia reckons to have this cracked. Reading though the obligatory slide show full of highlighted 'key' points that accompanies any product launch, we see that the Tegra 2 gives you roughly 100 times the power of a desktop per watt.

Each processing section has its job to do and anything not utilised is switched off or throttled right back.

HD playback at low power

The claims are impressive: HD video streams at under 150mW, as compared to multiples of this in the current rivals. Audio is similarly spare at under 50mW for MP3 playback.

Claims are just that until proved, but here we go: it says you can expect 140 hours of audio or over 16 hours of HD video, using a 2,000mAh battery.

While Nvidia is currently pushing the video capabilities to the fore, the sheer processing power of this chip deserves another mention. It's a dual-core chip that will end up in a phone for goodness sake!

Initial Tegra 2s will be billed as the Tegra 250 and run at a sprightly 1GHz. ARM currently has Cortex-A9s running at twice that, so there's headroom.

The Tegra 2 is the start of a comprehensive stab at the market, Nvidia reckons it'll be making major upgrades to it every twelve months. You'll be reading reviews of a Tegra device here very soon. We are prepared to be impressed.

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First published in PC Format Issue 240

Liked this? Then check out Nvidia's Fermi graphics architecture explained

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