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Rosewill Capstone-G1200 PSU Review

Efficiency, Temperature And Noise


Our efficiency testing procedure is detailed here.

Using the results from the previous page, we plotted a chart showing the Capstone-G1200's efficiency under low loads, and loads from 10 to 110 percent of the PSU's maximum-rated capacity.

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The ACRF topology doesn't facilitate impressive efficiency figures, so the Capstone-G1200 doesn't compare well to its competition, falling to last place in both graphs. Under normal loads, the difference isn't as large. However, under light loads, the Capstone unit is left behind. For context, Rosewill's Photon-1200, which bears the same 80 PLUS Gold rating and costs $10 less, outperforms the Capstone-G1200 at normal and light loads levels.

Efficiency At Low Loads

In the following tests, we measure the Capstone-G1200's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60 and 80W. This is important for representing when a PC is idle, with power-saving features turned on.

Test12V5V3.3V5VSBDC/AC (W)Efficiency%Fan Speed (RPM)Fan Noise dB(A)PF/AC (V)

Under light loads, our measured efficiency levels aren't high enough, though at just 80W of load the PSU passes the 80 percent mark.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher efficiency with 100mA of load, 60 percent or higher with 250mA of load and 70 percent or higher with 1A or more of load.

We will take four measurements: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle. 

Test5VSBDC/AC (W)Efficiency (%)PF/AC (V)

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The 5VSB rail yields a pleasant surprise. This is the first time we've seen such an efficient 5VSB rail, and as you can see in the table above, we crossed the 80 percent threshold in three of our four tests, the highest exceeding 85 percent.

Power Consumption In Idle And Standby

Mode12V5V3.3V5VSBWattsPF/AC Volts
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In the table above, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).

Phantom power is very low, improving the 5VSB rail's efficiency, especially under light loads.

Fan RPM, Delta Temperature And Output Noise

Our mixed noise testing is described in detail here.

The first chart illustrates the cooling fan's speed (RPMs), and the delta between input and output temperature. The results were obtained at 38 °C (100.4 °F) to 49 °C (120.2 °F) ambient temperature.   

The next chart shows the cooling fan's speed and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside our chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 38 °C (100.4 °F) to 49 °C (120.2 °F) ambient temperature. 

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The following graph illustrates the fan's output noise over the entire operating range of the PSU. The same conditions of the above graph apply, though the ambient temperature was between at 28 °C (82.4 °F) and 30 °C (86 °F).  

The graph looks like a mosaic, at least up to 650W, because the fan control circuit frequently made adjustments through the light and moderate load levels. Overall though, this is a noisy PSU that'll get loud enough to annoy you under tough conditions.