Tag Archives: Efficiency

Efficient Power Supplies: Part 1

Good morning!  This is an intro article…feel free to skip if you already know what efficiency means for power supplies.  Part 2 goes into detail of the 80 Plus standard and is likely a more enthralling read for you spec heads!

Let’s talk about the most important piece of hardware that a desktop computer can have…the power supply!  This little guy is responsible for electrifying all the goodies inside your computer.  Furthermore, a good power supply protects your computer from dirty power (voltage spikes, EMI ripple, power fluctuations, etc).  If you have ever read an article on custom desktop building, you probably know how crucial a good power supply is, as well as the consequences of using a cheap PSU.  Suffice it to say that, for the sake of your computer’s health, this is one area where you don’t want to skimp on cost.

There is one trait of quality power supplies that is often overlooked, and that is energy efficiency.  In a perfect world, a PSU would convert every watt of 120 V AC input power into usable DC power.  In reality a portion of the power is lost as heat.  The more efficient a power supply, the less energy it wastes as heat.  In other words, your computer simply draws fewer watts from the wall.

Having an efficient power supply is crucial for F@H contributors and non-folders alike, because it will make your computer less power hungry no matter what it is doing.  From gaming and graphics design to office work and Folding@Home, an efficient PSU will put a smile on your P3’s cute little face.  (If you don’t get the reference, please also read the previous post about Watt meters)

Before I go on, I should note that the target audience of this article is those who have built or are building their own custom desktop.  People with laptops or with name-brand consumer desktops are sometimes out of luck because the power supplies are often proprietary and can’t be upgraded.  However, it doesn’t hurt to find out from the manufacturer of your computer what the efficiency of your power supply is.  Some brands, such as Dell, HP, and Apple (among others) do have energy efficient power supplies of varying levels in their machines.

Cheap No-Name Brand Power Supply Unit that Came with a Case Bundle

Cheap No-Name Brand Power Supply Unit

If your power supply looks as lame as the one in the above pic, then it probably has an efficiency rating of 60 to 70 percent.  This means that if your computer parts need roughly 200 watts of power to run, your PSU might draw 250 watts or more from the wall in order to supply the 200 watts of DC power.  That extra 50+ watts is wasted as heat.

PC Power & Cooling SILENCER PSU

PC Power & Cooling SILENCER PSU

Seasonic SS-380GB PSU Installed

But, if your power supply looks like the one in Pic # 2 or #3, it might be closer to 80 or 90 percent efficient.  For that same 200 watt load, it is only drawing perhaps 220 watts from the wall.  The thirty watt difference might not seem like much, but for a Folding rig running 24/7 the wasted wattage of the el-cheapo unit adds up.  Let’s assume we are running a machine with the craptastic PSU.  To calculate the total extra energy wasted relative to the better PSU (remember, watts is a power quantity, which means energy/time), we need to multiply the wasted wattage by the amount of time the computer was in service to get an energy quantity in watt-hours.  So, 30 watts * 24 hours/day * 365 days/year = 262800 watt-hours.  Converting to kilowatt hours (dividing by 1000) gives 262.8 kWh.  Assuming an average electricity cost of ten cents per kWh, we get an annual cost of 262.8 * 0.10 $/kWh = $26.28.  Assuming the folding computer is running with that same power supply for 5 years (mine has been going for longer), that is over $125 wasted dollars, not to mention a slap in the face for poor planet Earth!  A good energy efficient PSU could have been bought for $40 in the first place to negate this wasted energy cost and lessen the environmental impact.

So how can you spot an efficient power supply unit?  Well, for that you can go by the independent test & certification program known as 80+.  I will cover this in detail in the next article, so that people who want to jump right into the specs and skip this intro can do so.

Efficiency Defined

Give Me Efficiency or Give Me an Empty CPU Socket!

You could always just remove your CPU to slash your power consumption, but no cancer gets cured that way.

Hi guys & gals!

Before I start talking the specifics of various computer hardware configurations, let’s get the definition of efficiency out of the way.  After all, computational efficiency is where it’s at!  That is the whole point of this blog.

Warning: Math Time (feel free to skip down a few paragraphs if you know this already):

Efficiency is a numerical ratio of two work or power quantities.  It has the general form of OUTPUT / INPUT.  Basically, it tells you how much desired work you got out of some process for a certain amount of input.  For a true mechanical or electrical efficiency, the units of both the numerator and denominator would be the same.  For example, our microwave at work generates 1200 watts of cooking power inside the machine, but draws 1488 watts at the wall.  Thus, it’s efficiency in terms of cooking power is: 1200 / 1488 = .806.  Multiply this fraction by 100 to get the efficiency percentage, and you see that our microwave is 80.6 % efficient at heating food.  Where did the rest of the energy go?  Well, in this case there was the power required to run the computerized guts, spin the turn table, spin the fan, light the light, etc.  There are also electrical losses in the circuits that get dissipated as heat into the microwave’s chassis.

Another good example is light bulbs.  In this case, we are looking at something called efficacy, not an electrical efficiency (but it is directly related), because the units in the numerator and denominator are going to be different.  It is possible, but less intuitive, to convert into a true efficiency ratio (visual power out / electrical power in), but I’m not going to go there because it hurts my brain.  Anyway, the good old 60 watt light bulb uses 60 watts (gosh) to create about 800 lumens of light.  By comparison, compact fluorescent bulbs use about 12-14 watts, and the new CREE LED bulbs use 9.5 watts.  Thus, the luminous efficacy of a 60 watt light bulb is 800 lm / 60 w = 13.3 lumens per watt.  On the other hand, the luminous efficacy of the awesome CREE LED bulbs (I have them everywhere in my house now) is 800 lm / 9.5 w = 84 lm/watt.  That is over 6 times more efficient than the old-fashioned tungsten filament bulb!  (Aside: you really should change out any 60 watt or 100 watt bulbs you still have in your house with CFL or CREE LED bulbs.  This is a great step towards negating your F@H carbon footprint! PLUS, IT  SAVES YOU MONEY!)

So, how does this relate to folding?  While, with F@H there is an accepted definition of work done, called Points.  The more work units complete, the more points you get.  Also, the faster your computer does the work units the more points you get (big time…it is exponential.  More on Stanford’s Points scheme later…).  So, to make this a power quantity (work done over time), we need to divide the # of points your computer is generating by the number of days it took to get those points.  Thus, we get to the most common rating of Folding@Home performance: The Points per Day unit (PPD).

We can obtain a rough “efficiency” of a F@H computer by dividing the PPD (scientific work output) by the electrical power (input) of the computer.  Note that this is really more of an efficacy rating (how effective something is at producing a desired output) but everyone on the interwebs calls it an efficiency so I will suppress the engineer in me and go with the flow of electrons on this one.

So, our F@H efficiency is PPD/Watt.  This is so central to this blog that I am going to say it again, for those skimmers who don’t like reading.

F@H efficiency is measured in Points Per Day / Watt!!!!

This is what we are concerned with.  Slow computers from 5 years ago still use a similar amount of electricity as today’s modern ones, but they are bricks when it comes to processing.  The amount of slow, crappy computers that are still running F@H is insane, and it is growing!  This is one of the main reasons why Folding gets a bad rap…the overall efficiency of the supercomputer as a whole is terrible.  We need to fix this!  Thankfully, Stanford & Sony have already ditched F@H on the Playstation 3.  This partnership was once one of the greatest boons to the F@H network, as back in the day the PS3’s were some of the fastest machines on the planet.  But, as computers got faster and the years went by, PS3’s became a poor choice relative to the new, super-efficient desktop processors and graphics cards.  Thus, F@H was removed as an option for Playstation users (much to their annoyance).  However, there is less management going on with the computer side of the F@H network (which is currently all of it).  If I want to, I can pull out my old Pentium 4 machine and get 100 PPD / 150 watts of power = 0.67 PPD/Watt!  But why would I want to spend money & kill the planet for that measly amount of performance?

I get the sense that you are likely getting the point by now, and thus I probably can stop rambling.  I can talk efficiency and specs all day (much to my wife’s annoyance).  The key takeaway is this:  Computers are always getting faster and more efficient.  F@H is as well, but is hindered by the amount of old computers that are stuck in yesteryear’s levels of efficiency.  We need to fix this.  We want to make our electrical contribution worth something.  WE WANT TO GENERATE AS MANY PPD/WATT AS POSSIBLE!  And that is exactly what we are going to do.  Over the next few posts, we’re going to talk in slightly less general terms about two things: how to Maximize PPD and how to Minimize Computer Power Consumption.  The latter is especially relevant to any computing project, even gaming or home computer use, so please feel free to read on even if you don’t plan to fold yourself.  Saving the planet and saving money by not using any more electricity than you need to accomplish a task is a worthy goal.  Tune in next time for the first hardware article: PC Power Supplies!