Power consumption and Vista’s Aero interface

Much has been made of Windows Vista’s new Aero interface, and for good reason. The GUI is loaded with luscious eye candy, including the liberal use of transparency, and even a few 3D effects. That eye candy doesn’t come cheap, though. Aero relies on graphics hardware to accelerate the interface, and requires a DirectX 9-compatible graphics card that supports Shader Model 2.0 and has at least 128MB of memory. Those requirements are pretty steep for an operating system, but they also raise an interesting question: if Aero is accelerated with graphics hardware, will system power consumption rise as a result?

Vista’s swanky Aero interface

Obviously, higher power consumption isn’t a good thing. For one, it makes a system more expensive to run. More importantly, though, it increases the amount of heat that must be dissipated by a chassis’ cooling configuration. The more heat you have to dissipate, the more cooling you need, and that can lead to higher system noise levels.

To determine whether running Vista’s Aero interface increases a system’s power consumption, I grabbed a copy of the latest public release candidate, x64 build 5728, and a stack of graphics cards that included a Radeon X1900 XTX and X1800 GTO, and a GeForce 7900 GTX, 7900 GT, and 7600 GT. Then, I put together a system with an Athlon 64 X2 5000+ processor, MSI K9N SLI Platinum motherboard, 2GB of Corsair DDR2 memory, Western Digital Caviar RE2 hard drive, and a 700W OCZ GameXStream 700W power supply and began testing.

This system was plugged into a Watts Up watt meter that measures system power consumption, sans monitor and speakers, at the wall outlet. Power consumption was measured under three scenarios. In the first, the system was left idling at the Windows desktop. Next, the system was left to idle with Windows Media Player and Internet Explorer windows open on the desktop. Finally, I measured peak power consumption while using Aero’s fancy 3D window switching feature.

For the first two scenarios, I measured power consumption with Vista’s Aero and Classic interfaces. The latter doesn’t have any fancy eye candy effects, so it makes a good baseline for comparison. However, the Classic interface doesn’t support 3D window switching.

Windows switching in 3D

I had plans to put together a bunch of graphs illustrating the results, but those wouldn’t have been terribly exciting graphs to read. With each graphics card, from the Radeon X1900 XTX down to the GeForce 7600 GT, system power consumption with Vista’s Aero interface was only marginally higher than it was with the Classic interface. A GeForce 7900 GT-equipped configuration, for example, idled between 105 and 106W with an empty Classic desktop, and 106 and 107W with two windows open. With the Aero interface, the same system idled closer to 106W with an empty desktop and closer to 107W with two windows open.

In all, none of our configurations consumed more than an additional watt moving from Vista’s Classic to Aero interface. Power consumption did spike by between 10 and 15W when using Aero’s 3D window switching feature, though. This spike didn’t last for much more than a second, so it’s unlikely to have a significant impact on overall system power consumption or noise levels. In fact, none of the cards we tested with variable-speed cooling fans even ramped up their fan speeds during our Aero testing.

Despite requiring a recent 3D graphics pipeline, Vista’s new Aero interface doesn’t meaningfully increase overall system power consumption. This is still a beta operating system with beta graphics drivers, of course, but it seems unlikely that power consumption will be a problem for Aero when Vista finally hits shelves.

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