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Load testing the PSU

Testing a PSU in theory it's not that difficult, stressing a 1200 Watt PSU, now that's a little different. Luckily three-way SLI and Quad Crossfire is just around the corner so in the future this stuff will be easier to measure.

But the fact is that we do not have the gear in house to be able to stress this PSU to it's full capacity. We can connect everything we want, add more devices and overclock, but even then we'd normally peak at 500-550 Watts. But hey, let's try that out and see what happens.

So here's what we did. We took:

• eVGA Force 680i SLI mainboard (consumes heaps of current)
• Core 2 Quad Q6600 Processor (overclocked to 3 GHz)
• 2x GeForce 8800 GTX cards setup in SLI (625c - 2100m)

After the installation we loaded the latest drivers, and enabled a seriously funky gaming experience on our power hungry system.

Now to stress a little more we overclocked the CPU cores towards 3.0 GHz, had the DDR2 memory running at 1147 MHz and the two GeForce 8800 GTX cards toward 625 MHz on the core and 2100 MHz for its memory.

For the test we used a combo of X3: the reunion & 3DMark 06. It's a total bitch on graphics cards; it makes them sweat. And recently I added Call of Duty 4 as it's also multi-core threading.

Where we could we enabled 8xAA and 16xAF to make sure the graphics cards were working hard. The balance of these settings also ensures me that that the CPU is utilized as much as can be. Now at this point I realized that we're stressing the PSU only slightly. So I added fan's, some extra lighting and water-cooling.

We monitored the primary voltages in both IDLE and LOAD (fully utilized) modes. We noted down the lowest and highest value we see and that is the fluctuation. If a PSU is unstable we'd see much fluctuation, differences and discrepancies which can result in system instability.

Now look at the animation, the orange line represents the Idle or Load state of a specific voltage rail; the yellow one, the highest fluctuation. A 5% fluctuation is perfectly acceptable and falls within ATX specification, so 12 Volts should remain between 11.4 - 12.6v as you can see the PSU when utilized stays FAR from that.

It is "RockSolid" stable. During the load test several times I felt to see if the PSU was warm, it remained cold at all times. It feels like it's hardly doing anything at all.

Very notable is this; wattage did not peak over 500 Watt where other PSU's did have much higher peak loads. Now please remember what I told you about power efficiency. This PSU's efficiency is really good and it's showing. We estimate between 80% and 85% efficiency.

Granted; it's really hard to stress PSU's like these. The fact that it remains stone cold at a near 500 Watt power draw however tells me that it can easily cope with the load.

Quite honestly, I did my best to stress the PSU. We are still awaiting gear from NVIDIA for a TRI SLI test which would ease our load test for sure. Yet in a 3D intensive test run with 100% utilization, in an overclocked environment this rascal is stable as can be.

Remember this was tested on a NVIDIA GeForce 8800 GTX (overclocked) SLI system with an overclocked (3GHz) Quad Core Q6600 processor.

Let's have a look at sound ... ehm, yeah, that's right.

Sound levels (dBA)

Well, the lack of it. As usual we grabbed our dBa meter, enabled the PSU by hot-wiring it and started to listen if it made any significant noise. Short and simple it's really silent. With merely the PSU hotwired and no other electrical devices activated in a closed room we measured a nice dBA level below 37 dBA.

The human hearing system has different sensitivities at different frequencies. This means that the perception of noise is not at all equal at every frequency. Noise with significant measured levels (in dB) at high or low frequencies will not be as annoying as it would be when its energy is concentrated in the middle frequencies. In other words, the measured noise levels in dB will not reflect the actual human perception of the loudness of the noise. That's why we measure the dBa level. A specific circuit is added to the sound level meter to correct its reading in regard to this concept. This reading is the noise level in dBA. The letter A is added to indicate the correction that was made in the measurement.

All in all, very silent and thus highly recommended to any of the audiophiles that like silence (yours truly included). As always we measure 75 CM away from the product (usually the distance between you and a desktop computer), and yes .. this test is always a tad subjective yet we measured ~37 DBa and that's including surrounding noise levels. That's just all right.

The Sirtec High Power 1200W Power Supply unit is exceptionally quiet.