Will Power Consumption Burn Vista’s Avalon Aero Graphics?

Wasted Power


I’ve been thinking a lot about power consumption in our PCs. Forinstance that a PC sitting idle, monitor(s) in standby mode, isconsuming 70W or more in many cases. All while doing nothing more thananxiously awaiting your return (if you’re silly enough to run somesort of 3D “screensaver”, that number increases significantly).

Often they’re idling around the clock on the off chance that youmight wander by and desire instant PC satisfaction. In thecorporate setting it’s frequently policy to leave workstations onaround the clock, for the infrequent occasion that the networkadmin team needs to roll out a patch.

In the former case you should look at standby or “hibernation”.In the latter case, the admins should be using Wake-on-LAN, whichis supported close to universally. Dated arguments about systemfailure or hard drives seizures on start-up aren’t rational, oreven statistically valid worries.

Increasing Consumption

Which brings me to online power consumption: the power yourcomputer is burning when it’s busy doing actually usefulwork for you. Over the past decade processor power consumption hasskyrocketed (with brief retreats, followed by the next surgeinto power gluttony). Thankfully, though, the power consumed by aprocessor does scale in a loose correlation with load: A processorat 100% utilization uses more power, and generates more heat, thanone idling, courtesy of various power saving strategies availableon modern PCs and operating systems (such as the HLT instruction).This is even more evident with mobile processors, which actuallyreduce the voltage under a lower processing load, saving even moreenergy (and thus reducing the heat output proportionately, as wellas the need for noisy internal fans).100_0084

These savings are offset, though, by the monsterco-processor that most PCs have: The videocard GPU, which offloads3D graphics operations to a hugely complex piece ofsilicon (video card GPUs are far more complex than your CPU in mostcases). Couple that with huge amounts of power-sucking ultra-highspeed onboard memory, and video cards are now pushing 150W+ of power consumption under a load (such as when running a1st person shooter). Thankfully modern video subsystem turn off asubstantial portion of their circuitry when it’s unneeded, such asin the 2D world when composing a document in Word, vastly reducingpower consumption.

Nonetheless when the demand is high and you add together theload of a processor running at 100% with a video card doing thesame, you have a recipe for a tremendous powersink that doubles as a competent space heater.

The end result of this power consumption is increased resourceusage, higher electric bills and demand on the grid, PCs thatrequire more fans and cooling solutions (and thus create more noisepollution), and often a hotter, less comfortable environment.

Even if you don’t care about the environment or rising powercosts, and if you enjoy the balmy 40C room temperature, when you’reusing a mobile PC the the lifespan of your battery, along with theability to use your laptop without it igniting your pants on fire,depends upon the efficient use of computing resources. In that caseyou absolutely want your processor and supporting systems (e.g.graphics GPU) doing the absolute least amount of workpossible to satisfy your requirements, doing whatmatters to you without wasting cycles with frivolity.

Windows Vista

Which brings me to Windows Vista (previously WindowsLonghorn).

One of the major new features of Windows Vista is the AeroGlass experience (both as an API for applications, and theshell itself). Aero Glass in essence turns your desktop into avideo game: Instead of the current model where the GDI draws on a2D palette, updating the video card memory (making use ofacceleration routines that the video card supports) only whenchanges occur, the model of Aero Glass is that of a traditional game: With every”frame” the scene is wiped clean and re-rendered from scratch,layering “textures” that represent application canvases onto 3-Dpolygons and building the user experience from there.

This system will attempt to push 60-90FPS of user experiencegoodness through your video card.

In many cases this will max out even high end video cards. Evenwhere it doesn’t, all of the shaders and T&L engines on thevideo card are engaged – the additional power consumption will beconsiderable. This could easily add 150W+ to your systempower load, and could absolutely devastate batterylifespan for portables. This is on top of the fact that you’resuddenly measuring your GUI in frames per second.

In other words the new, shiny user experience in Aero Glassisn’t just making use of unleveraged hardware in your PC(which is a valid point – there’s a big powerful graphics cardthere, so why should it go to waste) – It’s also considerablyadding to the power consumption, heat generation, and coolingrequirements. In the mobile world it would be hugely detrimental tothe battery lifespan.

All to add a bit of eye candy that, at least as far as I’veseen, marginally improves usability.