Windows 8 Gestures: Latency And Power Consumption
| Microsoft Surface | ||||||||
|---|---|---|---|---|---|---|---|---|
| Row 0 - Cell 0 | Delay (ms, Lower is Better) | Frame Rate (FPS) | Platform (W) | CPU (W) | GPU (W) | Memory (W) | Panel Backlight (W) | Everything Else (W) |
| Bing Maps (Split-Screen / Pinch) | 133.3 | 38 | 6.06 | 1.07 | 0.97 | 0.77 | 0.98 | 2.27 |
| Bing Maps (Split-Screen / Drag) | 125 | 45.6 | 5.80 | 0.80 | 0.76 | 0.96 | 0.98 | 2.30 |
| Bing Maps (Split-Screen / Flick) | 175 | 57.6 | 5.65 | 0.98 | 0.92 | 0.60 | 0.99 | 2.16 |
| Wikipedia (Split-Screen / Pinch) | 158.3 | 55.3 | 5.28 | 0.97 | 0.75 | 0.47 | 0.99 | 2.10 |
| Wikipedia (Split-Screen / Drag) | 183.3 | 57.2 | 4.92 | 0.70 | 0.72 | 0.46 | 0.98 | 2.06 |
| Wikipedia (Split-Screen / Flick) | 183.3 | 60 | 4.89 | 0.66 | 0.70 | 0.49 | 0.99 | 2.07 |
| Acer W510 | ||||||||
|---|---|---|---|---|---|---|---|---|
| Row 0 - Cell 0 | Delay (ms, Lower is Better) | Frame Rate (FPS) | Platform (W) | CPU (W) | GPU (W) | Memory (W) | Panel Backlight (W) | Everything Else (W) |
| Bing Maps (Split-Screen / Pinch) | 83.3 | 33.8 | 5.50 | 0.76 | 0.50 | 0.54 | 1.24 | 2.47 |
| Bing Maps (Split-Screen / Drag) | 91.7 | 42.4 | 5.36 | 0.72 | 0.55 | 0.55 | 1.25 | 2.28 |
| Bing Maps (Split-Screen / Flick) | 116.7 | 56.2 | 4.96 | 0.58 | 0.45 | 0.49 | 1.23 | 2.22 |
| Wikipedia (Split-Screen / Pinch) | 75.0 | 53.7 | 5.07 | 0.82 | 0.34 | 0.44 | 1.28 | 2.19 |
| Wikipedia (Split-Screen / Drag) | 150 | 59.2 | 4.76 | 0.64 | 0.31 | 0.44 | 1.26 | 2.10 |
| Wikipedia (Split-Screen / Flick) | 83.3 | 56.5 | 4.53 | 0.59 | 0.32 | 0.42 | 1.26 | 1.94 |
Finally, we get a glimpse of power consumption during touch-based gestures using the Windows 8 UI on Bing Maps and Wikipedia using a split-screen configuration. This is the sort of thing you'd never be able to quantify without fancy equipment, but would almost certainly notice using both devices one after the other.
Not to belabor the point, but look at the memory controller numbers again. The Atom’s power consumption remains stable, regardless of the workload, whereas the Tegra 3’s consumption increases alongside complexity. Acer's W510 actually uses more power than the Surface elsewhere. But because its CPU, GPU, and memory controller are more efficient, total platform consumption is lower than Microsoft's.
In the upcoming piece on Acer's W510, we'll discuss some of the optimizations Intel made to its memory controller specifically to improve touch responsiveness at the expense of synthetic benchmark performance. In this case, the first column tells us that the delay for detecting a gesture is shorter (faster) on Acer's tablet than Microsoft's every single time. The best-case scenario for the Surface is still slower than five out of the six gestures tested on the Atom. However, the Surface yields generally-better frame rates. If you look at a Wikipedia pinch, the Atom allows the frame rate to drop 3%, but yields a latency that's twice as fast. The Surface is 11% faster in a Bing Map pinch, but incurs a delay 60% higher.
