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Old July 14, 2009, 06:12 AM
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SKYMTL SKYMTL is offline
HardwareCanuck Review Editor
Join Date: Feb 2007
Location: Montreal
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Power Supply Testing Methodology

Sub-700W PSU test system has not yet been determined.

Test System Setup

Processor: Intel Core i7 920(ES) @ 4.0Ghz
Memory: Corsair 3x2GB Dominator DDR3 1600Mhz
Motherboard: Gigabyte EX58-UD5
Graphics Card(s): HD4870X2 Single and Crossfire (@stock speeds)
Cooling: CoolIT Boreas mTEC + Scythe Fan Controller
Disk Drive: Pioneer DVD Writer
Hard Drive: Western Digital Caviar Black 640GB
Additional Fans: 2x Yate Loon 1200RPM
Monitor: Samsung 305T 30” widescreen LCD
OS: Windows Vista Ultimate x64 SP1
* Open test bench

So, what do we use to test these power supplies? Read on...

Load conditions

In these sections we will be detailing how we load the tested power supply in order to determine how it performs in certain conditions. We try to gradually increase load with realistic tests which a consumer may experience with their unit. Usually, the last test is reserved for a "worst case scenario" which is used to stress the system far beyond what a normal user would experience.

It has only been after extensive testing of dozens of programs that we came up with programs / combinations of programs that put the MOST stress on our components. It is only the programs which consumed the most amount of power that we are using for our load conditions.

*Each test is run over the course of 30 minutes.

*Please note that the Crossfire setup is only used for 900W and higher PSUs

*Unless otherwise noted, the Boreas TEC runs at a constant 100%

Idle Conditions

Off: Is a load value where the system is turned off but a small amount of power is still required.

Idle: Idle values are determined by a stable Windows Vista x64 desktop.

Idle + TEC: Reflects an idle conditions mentioned above but with the Boreas TEC’s running at 100% load

Idle + CF: Same idle conditions as indicated above with a pair of HD 4870X2 cards installed.

Load Conditions

CPU Load: This test is run with 8 instances of a custom Prime95 test which we have found uses the most non-GPU power. The test is run for 30 minutes.

GPU Load: For this test we are aiming to show power consumption in a typical fast-paced gaming scenario. As such, we load a single HD4870X2 with custom timedemo of Far Cry 2 at 2560 x 1600 with 4x AA enabled and set it to loop for approximately 30 minutes.

Max Load: For this test we use the single GPU setup running 3DMark06 Batch Render Test at 2560x1600 4xAA / 16xAF while running our custom Prime95 test on the CPU in the background. Once again, this is a 30 minute test.

Extreme Load Test: This is the big one which separates the boys from the men. Basically, it is the same test as the Max Load test but we add another HD4870X2 into the mix and test for 30 minutes.

Voltage Regulation Testing Methodology

Voltage regulation is a very important aspect of every power supply in the sense that it can affect the stability and safety of your system. If the voltages dip too low, you can experience everything from crashes to unstable overclocks. The ATX specifications dictate that the rails of a power supply should be regulated as follows:

+12V Rail(s)

Normal: 12.00V
Min: 11.40V
Max: 12.60V

+3.3V Rail

Normal: 3.30V
Min: 3.14V
Max: 3.47V

+5V Rail

Normal: 5.00V
Min: 4.75V
Max: 5.25V

Testing voltage regulation is a must in any power supply review. Testing with software is inaccurate at best so we have chosen to go with industrial-grade multimeters which are calibrated every 3 months by an ISO-certified local electronics distributor. This one calibrated multimeter is used as a benchmark for all of the other multimeters in our lab; they all have to read within 0.02V of the calibrated multimeter or they too are sent for calibration.

Multimeters Used:
Extech 430 DMM x3

*Note: All voltage readings indicated in the review are the minimum voltages seen over the period of our tests

Many review sites take their voltages from an unused Molex connector but we do not. Rather, we always take voltage readings from a loaded connector in order to more accurately see the voltage fluctuations our components are experiencing. Thus, this is how voltages are measured:

+12V: In the CPU Load test the voltages are taken directly from the CPU connector of the power supply. In the GPU Load test the voltages are taken from an 8-pin PCI-E connector which is plugged in to the topmost graphics card. In the Extreme Load test, readings are taken from both the CPU and the PCI-E connectors and the lowest reading is recorded.

+3.3V / +5V: From the main ATX connector. All voltages are the lowest recorded over the test period.

AC Ripple Testing Methodology

AC Ripple (or noise as it is also called) is one of the most under-measured aspects of a power supply's performance that we have come across. Among the few sites we have come upon that actually measure it, only a bare minimum measure it with any accuracy. Yet, this one measurement is as important as voltage regulation.

A high amount of ripple coming from the power supply's rails can be detrimental to the stability and longevity of your system. While many motherboards, graphics cards and other components may not see any immediate effects of excess ripple, it can contribute to wear down your components' lifespan significantly. Some may wonder why their ram suddenly stops working while others may scratch their heads at why a previously stable overclock has become unstable after a few months. Some of these cases can be traced back to excess ripple.

These are the ATX specifications regarding ripple:

+12V : 120mV Max
+3.3V: 50mV Max
+5V: 50mV Max

We believe that the ATX specifications for the +12V rail are set far too high and thus will consider anything over 100mV a failure. All ripple measurements given are the highest recorded over the test period. The values were the highest peak ripple measurement across all of the +12V rails. So, if the +12V1 rail shows a ripple of 20mV and the +12V2 rail shows a ripple of 40mV, the highest value will be graphed.

Instruments Used:
USB Instruments Stingray Digital Oscilloscope
USB Instruments Differential Oscilloscope Probe

Here is where we have spent the majority of the money when it comes to testing equipment and time learning how to use it. Basically, the Stingray is plugged into a laptop and is used to determine AC ripple (among other capabilities) emanating for the power supply's rails. Since we do not have a load tester with a BNC connector for the standard o-scope probe, we needed a Differential probe in order to give us the proper capacitance to accurately determine ripple. In addition, the differential probe has a pair of connectors which are very much akin to a multimeter's probes which makes them ideal for use on SMPS designs. The locations of the probes for each test reflect the locations of the multimeter probes detailed in the Voltage Regulation Testing Methodology section.

Efficiency Testing Methodology

In the last year or two, efficiency has become more and more important in the realm of power supplies as consumers have become more attuned to the environmental impact of consuming copious amounts of electricity. Not only has the cost of electricity gone up dramatically but the power consumption of modern computers is hitting all-time highs as well. Lower efficiency means more power being wasted as heat inside of a power supply and because of this the overall heat signature of a computer will increase as efficiency decreases. In addition, because of this increased heat, the fan on the power supply has to ramp up as well in order to keep the sensitive components cool. It is all a vicious circle with only one thing being painfully obvious: the higher the efficiency the better.

The few websites that measure efficiency are able to give you a percentage (ie: 80% efficiency) based on the difference between actual DC load (the power consumption of your components) and AC power consumption (the amount of electricity being drawn from the wall). Unfortunately, we have no accurate way of knowing how much load our components actually consume so there is no way of coming up with an accurate percentage figure. So, we have much more realistic goals: to compare the power supply being reviewed to the best we have tested in the past in the same category in terms of AC power consumption.

Instruments Used:
UPM Power Meter
Tripp Lite LC1800 Line Conditioner

What the UPM power meter does is give us how much power the entire system is drawing from the wall at any given point. The data points you see in our charts show the AVERAGE PEAK AC power consumption over all of the tests conducted.

Temperature Testing

Considering the amount of heat our open-air test system produces, it was found to be nigh-on impossible to properly regulate the temperature in the room even with a 10,000 BTU air conditioner. As such, we will be measuring the delta between room temperature and the exhaust temperature from the power supply.

To test temperature, we set up a pair of Type-K temperature probes. One is placed in the middle of the testing room at an elevation of 5 feet AFF to measure ambient temperatures. Menwhile, the other temperature probe is placed 4” away from the exhaust grille of the power supply.

A few other tidbits

- AC Input Voltage: 120V constant
- Noise is subjectively tested

Last edited by SKYMTL; July 14, 2009 at 07:26 AM.
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