Efficiency measurements, then vs now, comparable?

[wwenze]

I would like to ask, the measured efficiencies in long-ago SPCR PSU reviews, can they be used for comparison against those of the more recent reviews, say, those within the past year or two.

Reason I'm asking - I got an Antec Truepower New which I can either sell or replace a Seasonic S12. I'm guessing that an undervolted X3 720 and HD5670 will never exceed 150W so I'm looking more at efficiency at 90W and 65W.

However only a few PSUs managed to do better than the S12 in this regard - most are either about the same or slightly less.
http://www.silentpcreview.com/article1008-page5.html
http://www.silentpcreview.com/article994-page4.html
http://www.silentpcreview.com/article971-page5.html
http://www.silentpcreview.com/article970-page5.html

PSU - 65W, 90W, 150W
Seasonic S12 - 78.3, 80.5, 81.6
Corsair CX400W - 77.8, 81.2, 82.1
Enermax Eco80+ - 77.1, 80.2, 82.0
Antec CP-850 - 73.9, 81.6, 83.2
Nexus RX-8500 - 71.6, 75.4, 80.0
I would've expected PSUs to have become more efficient, so I'm not believing what I'm seeing here. Unless the numbers are not comparable.

[frostedflakes]

If you look at 20%, 50% and 100% load, modern PSUs should be more efficient. S12 was a nice PSU during its day, but modern 80Plus Bronze, Silver, and especially Gold designs are better. When you plot power supply efficiency, it will have a curve with efficiency dropping off slightly as you approach 100% load and dropping off sharply as you approach no load. Peak efficiency is at around 50%. This means that smaller power supplies are generally better for smaller loads. Buying a 430w and loading it to 20% is better than buying an 850w and loading it to 10% from an efficiency point of view. There are exceptions, though. For example, the new Seasonic X-650 would be an excellent choice even for a low power system. Even at low loads it's amazingly efficient, it runs cool, and the fan doesn't even turn on until you put a few hundred watts of load on it. PicoPSU and an external brick is another excellent choice if you have a very low power system and wouldn't need more than 100w or so.

What would be even better is a 300-400w 80Plus Gold PSU. Unfortunately these aren't available through retail channels (although Seasonic has a fanless 400w 80Plus Gold unit in the works), although some OEMs use lower wattage, Gold certified PSUs. A couple members have modified Dell RM112 units to fit in a standard case, see here.

viewtopic.php?t=57238

[wwenze]

I just realized, Bronze would need 82% efficiency @ 20% load, meaning 110W for a 550W Truepower New. Which makes it more efficient than all the abovementioned PSUs already.

But this is not what I'm asking - for example, a PSU was measured to be 80% @ 100W in a 2006 review, another PSU was also measured to be 80% @ 100W but in a 2009 review. Are the two PSUs as efficient @ 100W or was there any change in procedure/equipment over the years to render the comparison invalid?

[Tephras]

The PSU test rig are described here. Last change was in December 2006.

[dhanson865]

Code: Select all

PSU            -  65W,  90W, 150W
Seasonic S12   - 78.3, 80.5, 81.6
Corsair CX400W - 77.8, 81.2, 82.1
Enermax Eco80+ - 77.1, 80.2, 82.0
Antec CP-850   - 73.9, 81.6, 83.2
Nexus RX-8500  - 71.6, 75.4, 80.0

tables like that are much more readable if you use a text editor like notepad to lay them out then use the "quote" tags when you post.

And yes the numbers are comparable but you didn't pick the best. Did you pick by review date or by price or what?

I hadn't updated these in years but I just added two newer models today. You'll see that there are models that beat the snot out of the old S12 even at low wattage.

Code: Select all

Model       Output (W)  65      90      150     200     250     300   380/400/430/450 80Plus
        Efficiency                                                    as appropriate
Nexus Value 430         76.5%   80.7%   82.1%   83.7%   82.8%   82.7%   79.7%         None
     Corsair VX450W     79.1%   80.1%   82.6%   84.8%   83.3%   83.0%   81.8%         80Plus
Nightjar ST45NF 450W    77.3%   80.8%   82.6%   87.7%           87.1%   83.3%         Bronze
Enermax 87+ 500         84.1%   85.9%   88.5%   90.6%   90.5%   90.2%   87.6%         Gold
Seasonic X-650          82.6%   86.6%   88.3%   90.8%   91.7%   91.7%   88.8%         Gold
Seasonic M12D 850W      77.8%   81.6%   83.9%   87.5%   87.4%   87.3%   87.9%         Silver

         Temp Rise (°C)
Nexus Value 430                  5       4       4       5      10      15
Corsair VX450W                           4       7       9      11      16
Nightjar ST45NF 450W             4       5       8              10       9
Enermax 87+ 500                  5       7       8      12      14       9
Seasonic X-650                   5       5       4       5       7       8
Seasonic M12D 850W               4       5       8       9      10       9

         Noise (dBA@1m)
Nexus Value 430                 11      11      16      18      18      19
Corsair VX450W          noise numbers for this review were preanechoic chamber
Nightjar ST45NF 450W             0         Nightjar ST45NF is fanless    0
Enermax 87+ 500                 11      11      11      11      14      20
Seasonic X-650                  10      11      12      14      16      31
Seasonic M12D 850W              14      14      14      14      14      24

Code: Select all

Parameters  Load@ 80 Plus Bronze Silver Gold  90 Plus
             20%    80%    82%    85%    87%    90%
Efficiency   50%    80%    85%    88%    90%    90%
            100%    80%    82%    85%    87%    90%

You'll notice the Corsair VX450W beat the old S12 but you also have to realize the "S12" is a moving target

There were 3 revisions of the first S12
Then there was the S12 II
Then the S12 II Bronze

Which one are we comparing to in your case?

You'll notice I don't have the S12 II Bronze efficiency numbers here as SPCR hasn't reviewed that unit. I could try to pull those numbers from other sites but they often don't do the tests at the same wattage that SPCR does.