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Asus' Eee Pad Transformer Prime tablet

Optimus/Superman slash fiction

Do a Google image search for Transformer Prime, and you'll be inundated with pictures of this guy. Optimus Prime was the leader of the Autobots of my childhood, and I may or may not have cried when he died in the first movie (Transformers: The Movie—not the tripe Michael Bay has spewed out in recent years). You'll have to scroll through three pages of search results to come across the first picture of Asus' Transformer Prime, an altogether different machine.

Hasbro isn't pleased with the association, which Asus has admittedly made pretty blatant. One might be tempted to chide the company for tugging at the childhood nostalgia of geeks everywhere, but the Transformer name has been a good fit for Asus' first attempt at an Android-based tablet. With the addition of an optional keyboard dock that offers a proper touchpad, extra expansion slots, and another six hours of battery life, the Transformer turns into something that behaves more like a real notebook.

The Transformer Prime follows the same formula as its predecessor while offering plenty of refinements throughout. It's thinner and lighter than the original despite housing a more powerful Tegra 3 processor with five ARM cores and beefier GeForce graphics. Asus has updated the screen, the casing, and just about everything in between, including the operating system. The end result looks like the most impressive Android device to date, so we've spent some quality time with one to see what all the fuss is about.

There's a new Tegra in town
One of the most intriguing parts of the Prime is its Tegra 3 processor, otherwise known as Kal-El. This Nvidia system-on-a-chip succeeds the Tegra 2 found in the original Transformer and quite a few other Android-based tablets. Both chips are based on the same ARM Cortex A9 CPU architecture, but the Tegra 3 is a more robust implementation. Unlike previous Tegra processors, the third-gen chip's CPU cores feature ARM's NEON media engine. This dedicated SIMD unit supports extensions to the base ARM instruction set targeted at improving multimedia, graphics, and gaming performance.

In addition to beefing up its Cortex A9 cores, the Tegra 3 has more of 'em running at higher speeds. While the Tegra 2 sports dual cores, the Tegra 3 features a funky quad-core design with an additional "companion core" optimized for low power consumption. This fifth core has an identical ARM architecture to the others, but it tops out at just 500MHz. The Tegra 3 is capable of running its other four cores at speeds up to 1.3GHz, a 100MHz boost over its predecessor. And, thanks to a little Turbo-style mojo, the Tegra 3 can hit 1.4GHz if just one of those cores is active.

All five of the Tegra 3's CPU cores occupy a single piece of silicon fabricated by TSMC on a 40-nm process. The companion core uses transistors with very low leakage power but also relatively slow switching speeds, which is why it tops out at 500MHz. The other cores are optimized for higher switching frequencies and are capable of nearly three times the speed of the companion core at the same voltage level. As one might expect, these faster cores suffer from higher leakage power.

According to Nvidia, it takes less than two milliseconds to switch the Tegra 3 between companion and quad-core modes; the two core components are never active at the same time. "Aggressive power gating" is employed for each individual core, including those within the quad-core cluster, allowing the chip to cut power to dormant cores. There's also plenty of dynamic clock scaling at work, although Nvidia notes that active members of the quad-core cluster will all run at the same speed to ease OS scheduling.

The Tegra 3 block diagram. Source: Nvidia

The Honeycomb version of Android that ships on the Transformer Prime isn't aware of the Tegra 3's novel approach to symmetric multiprocessing, which Nvidia has dubbed variable SMP, or vSMP. To manage the chip's unique core composition, Nvidia uses a mix of hardware and software to monitor system activity and to adjust the core configuration appropriately. The companion core is intended to be sufficient for background tasks like email syncing, Facebook updates, and multimedia playback, while the quad-core block is reserved for gaming, web browsing, Flash, and other demanding tasks.

Nvidia claims the Tegra 3's dedicated decode hardware is powerful enough to handle all manner of multimedia playback without the aid of the chip's quad CPU cores. All the major codecs are supported at resolutions up to 1080p, and little appears to have changed from the previous iteration of the chip. The only notable addition I can find regards high-profile H.264 content, which the Tegra 3 can purportedly process at bitrates up to 40Mbps. Nvidia makes no claims about the Tegra 2's support for high-profile flavors of H.264.

The green team has been relatively tight-lipped about the GeForce graphics processor incorporated in the Tegra 3, too. Called only an "Ultra-low power GeForce GPU," this graphics processor has 12 cores and the ability to generate stereoscopic 3D images. We don't know the clock speed of the GPU, but Nvidia claims it offers up to three times the performance of its predecessor, which has only eight cores and doesn't support stereo 3D. The two implementations appear to be based on the same graphics architecture, so higher clock speeds likely account for much of the Tegra 3's advantage. This latest Tegra chip also supports higher memory frequencies than the Tegra 2, which should provide more bandwidth to the graphics subsystem.

Processor Nvidia Tegra 3 1.3GHz with GeForce graphics
Display 10.1" IPS TFT with 1280x800 resolution
Memory 1GB
Storage 32GB
Ports 1 Micro HDMI
1 analog audio headphone/mic port
1 USB 2.0 (dock)
Expansion slots 1 Mini SD
1 SD (dock)
Communications 802.11n Wi-Fi
Bluetooth 2.1+EDR
Camera 8-megapixel rear with LED flash
1.2-megapixel front
Input devices Capacitive touchscreen
Chiclet keyboard with touchpad (dock)
Dimensions Tablet: 10.4" x 7.1" x 0.33" (263 x 181 x 8.3 mm)
Dock: 10.4" x 7.1" x 0.41" (263 x 181 x 10.4 mm)
Weight Tablet: 1.29 lbs (586 grams)
Dock: 1.18 (537 grams)
Battery Tablet: 25Wh lithium-polymer
Dock: 22Wh lithium-polymer

As with the original Transformer, the Prime pairs its Tegra processor with a gig of RAM. That's double the memory of the iPad 2, whose A5 CPU looks considerably less powerful on paper. The A5 has only two Cortex A9 CPU cores clocked at 1GHz, so it's down both cores and clock speed versus the Tegra 3. Comparing the Apple chip's PowerVR graphics processor to the Tegra's integrated GeForce isn't quite as straightforward because the two don't share a common architecture. We'll see how they shake out in a handful of graphics tests a little later in the review.

The truth is that these little technical details don't tell us as much as we might like about how the Transformer Prime performs in the real world. It should certainly be faster and more responsive than devices based on the last-gen Tegra processor, but only because they're all running Android. Loading up on processing resources doesn't necessarily give the Prime a leg up on the incumbent iPad 2, which has an entirely different operating system—one that's long been the standard for overall responsiveness.

Our own Editor-in-Chief can't stop gushing about how much iOS 5 improved his iPad 2 experience, so it's worth noting that a major Android update is due to hit the Prime on January 12. The tablet ships with the older Honeycomb version of the OS, but Android 4.0 is coming via an over-the-air update next week. Otherwise known as Ice Cream Sandwich, this next version of the OS promises all sorts of enhancements, including improved performance and a new browser.

The Transformer Prime admittedly feels a little incomplete without Ice Cream Sandwich onboard. Fortunately, there's plenty to explore about this tablet beyond its software payload.