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Consider the system

Comments(2)Filed under: Low power , power

This may be slightly outside the scope of logic design, but since reducing power consumption is something that we are all concerned with, I thought this was interesting.  Check out the power consumption of various electronic products, in-use, “off”, and idle:

 

Nintendo WiiMicrosoft Xbox 360Sony Playstation 3
 OffOn, idleOn, playing a gameOffOn, idleOn, playing a gameOffOn, idleOn, playing a game
Energy (kWh)16.65155.09163.8621.061228.821355.8415.531655.201738.39
Cost @ 15c/kWh$2.50$23.26$24.58$3.16$184.32$203.38$2.33$248.28$260.76

(Full article here)

The article says that leaving a PS3 on, but not in-use, costs 5x as much electricity as running a refrigerator.   That's eye-opening.  1 PS3 > 5 refrigerators.

Not to pick on Sony - after all, the Xbox 360 consumes  almost as much power, and both systems offer incredible graphics, performance, and lots of features.  And the design teams’ top priorities were probably first to deliver on that performance, and second to meet the market window (both were November releases!).

But there are some power-hungry components in these things – an amped-up processor, GPU, hard drive, DVD player, WiFi, etc.  If you’re designing the GPU for one of these, you’re probably only focusing on the best performance.  After all, that’s the “wow” factor, and even if you save 50% power on your chip, there are all these other power-hungry devices in the system so that 50% gets watered down.

Perhaps the system itself should do a better job of managing and shutting down components, or the system itself, due to inactivity.  Better yet, since the software knows what mode the box is in – require each of these components to be controllable by-mode.  Of course, that takes planning and coordination, and adds a lot of complexity to something that you need to get into volume production ahead of a hard ship date.  And what happens if there’s a bug?  A recall would be deadly.

Or maybe we start to consider the human as part of the system.  After all, if they would just turn off the power then the problem is solved.  It’s not much harder than turning off a light bulb.  Of course, people constantly leave unnecessary lights on.   

So I come back to a simple approach – provide feedback.  If you’ve ever been given a demo of a Toyota Prius by one of its owners, you’ve surely been shown how you can monitor the mileage you’re getting.  And you’ve probably been told stories about how they pay attention to that and try different things to maximize it.  So why don’t we put power meters on our consoles?  Or even on our light bulbs?  Show how much they are consuming, in terms of dollar cost (after all, economic incentives are most powerful).  Yes, it will actually consume some power to do this, but the behavior change should dwarf that cost.  Provide feedback to the master of all system power controllers – the human.

In any case, power savings is often best looked at from the perspective of the entire system.  It really helps identify the largest impacts, and often the solution is simpler than adding lots of complexity at the chip level.  We can definitely do better than 5 refrigerators.

In the meantime, shut off those gaming consoles when not in use so we can all keep our beer cold!

Comments(2)

By Rich Owen on October 17, 2008
Nice post!
This is an area that is getting increased interest.  One nifty little device is the Kill-A-Watt (www.p3international.com/.../P4400-CE.html).  I keep meaning to get one - I'm sure it would complain like mad about my PS3.
When searching for the above, I came across a story from the UK.  They're planning on giving everyone free real-time energy meters.  The thought process is exactly as described above - if people know how much energy is being consumed, they'll do something about it.
There's an opportunity lurking here to provide near real-time power information from household appliances.  Maybe it is built in to the power unit, maybe it is a plug in device.  Either way, it could communicate to your home PC, giving you higher control over where you spend your household energy.  Is there a standard for this?  Should there be?

By BobD on October 20, 2008
Very interesting piece, Jack.  It is amazing how much less power the Wii consumes.  Its base price is less than the others and that evidently gets compounded year over year as the others gobble up more power!  Now, if only I could find a Wii available for the sticker price of $249. :)  On the subject of energy meters, I heard an interesting story on NPR a few years back referring to energy orbs: www.inhabitat.com/.../the-energy-orb-monitor-your-electricity-bill  Similar conceptually to the meter Rich pointed out, but I seem to recall there being optionally some sort of "social" aspect to the orbs whereby friends and neighbors could be informed of your power consumption if you placed the orb in the window, or if your E-mails, blogs, and online status reflected how well you were doing on conserving energy.  Awareness is the first step, but on top of that shame can be an incredible motivator!

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