Nvidia's Tegra 3 SoC, armed with four Cortex-A9 cores, powers Microsoft's first tablet.
Now, we've seen Tegra 3s running at different speeds. Google's Nexus 7 and Asus' Transformer TF300 both come with T30Ls, while the Transformer TF201 had a T30 in it. The SoCs are functionally similar, but the latter operates at 1.4 GHz, while the former has a peak clock rate of 1.3 GHz. Given that the Task Manager cites a 1.3 GHz ceiling on the Surface, we're pretty confident that we're dealing with the T30L.
According to the benchmarks we generated for Snapdragon S4 Pro: Krait And Adreno 320, Benchmarked, the Tegra 3 no longer goes uncontested in raw performance metrics. However, it still ranks near the top in GeekBench, and the SoC's graphics subsystem is middle-of-the-road. Qualcomm's S4 Pro most definitely enjoys the spotlight for now, thanks to its Krait cores. Nvidia won’t have its own SoC (currently code-named Wayne) based on ARM's Cortex-A15 until 2013.
The Surface doesn't feel underpowered, though. To the contrary, it's really snappy. We had to run SunSpider in IE 10, Word, and Excel all at the same time to get Tegra 3's processor utilization up near 100%. Opening up five browser tabs in quick succession triggered some stuttering, but hardly what we might have expected after reviewing Windows 8 less than a week ago on much more powerful x86 hardware.
Microsoft's Office team published a very interesting blog post describing some of the ways it tuned Office for Windows RT to recognize ARM as a "first-class" platform. This involved a lot of the features found in the x86-based version, but with tweaks to timers (yielding better utilization of battery power) and hardware acceleration of tasks, when possible.
|Kal-El||Companion CPU Core||Main CPU Cores (Symmetric Processing)|
|# of Cores||1||4|
|Process Technology||Low-Power (LP)||General|
|Operating Frequency||0 MHz to 500 MHz||0 MHz to Max Frequency|
The Tegra 3 SoC sports a fifth “companion” CPU core that operates at lower frequencies and handles background tasks like syncing email, playing ringtones, and keeping applications alive while the device is in standby mode. It'd be hard for us to quantify the benefits of Nvidia's architecture since there aren't any Tegra 3s without that fifth core. Needless to say, though, Microsoft was impressed enough by the hardware foundation to go with Nvidia for its first tablet. Minutiae aside, that's really what matters most.
Nvidia's fifth CPU core is transparent to the operating system. As a result, low-overhead tasks have to be identified by the SoC and specifically directed to the companion core.