As noted, we always have a bit of a challenge at hand. Without professional load testers it's pretty hard to stress a 600+ Watt power supplies.

So here's what we did. I decided to take a somewhat dated yet power hungry nForce 790i SLI motherboard. Then we take two GeForce GTX 295s (that's four GPUs) to maximize power consumption.

Now we again take a power hungry item, an Intel Core 2 Quad QX9770 processor and overclocked it towards 3600 MHz with some added voltage inside the processor. Now we overclocked our memory as well, again with added voltage.

These are the components used:

• nForce 790i motherboard (has high power consumption
• Core 2 Quad QX9770 Processor (overclocked to 3.6 GHz)
• 2x GeForce GTX 295 primary (4 GPUs)
• 4 GB Memory DDR3 @ 1600 MHz
• Optical Drive x1
• HDD x1
• Liquid Cooling loop

So here's where we start a selection of gaming tests well balanced for optimal CPU (multi-core) and GPU performance. We take a multi-meter and tap critical points when the system is under load and when in idle. We then observe the voltage fluctuation. A lot of de/increases would indicate instability.

For our test we used several combos of software including the Cryostasis Demo and 3Dmark Vantage which allows us to go hard on the GTX 295 (Quad SLI). During the test runs we simply monitor voltage fluctuations and our Watt meter registers maximum load measured.

Now with the older PSUs rated at say 70-75% efficiency we'd reach 700 Watts power consumption. But with power supplies getting more and more efficient these days, that proves to be a very hard task to accomplish.

Check that out, a long time ago this test would result into roughly 650 Watts power consumption for an 80% efficient power supply. With the new Gold certified Enermax Modu87+ that number already dropped towards roughly 575 Watts.

As an example, let me show you the results of a 700W Gigabyte Odin PSU we recently tested with the very same components and tests, that PSU was measured as being 83% efficient.

This is literally the difference we are measuring in terms of power draw measured from the wall socket. That's how important efficiency is. The new high-efficiency PSUs can shave off 50 to 100 Watts consumption under high load compared to an older model PSU from say 2-3 years ago.

Some additional notes here. Powered down the PSU consumes very little current, we measured 1~2 Watts only. And again, though we had so much gear plugged into this system, the power consumption remained fairly low, making me believe that 90% power efficiency is very plausible.