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Efficiency, Temperature & Noise
Efficiency
Our efficiency testing procedure is detailed here.
Using results from the previous page, we plotted a chart showing the TX750M's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.
The TX750M's efficiency is satisfactory, however it is no match for higher-end EVGA G3 and Corsair RM750x models. Our average efficiency graph shows the entire TX-M family finishing in order of highest to lowest capacity, with the TX850M on top.
Under light loads, though, the opposite is true...
Efficiency At Low Loads
In the following tests, we measure the TX750M'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.
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed | Fan Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.209A | 0.491A | 0.482A | 0.196A | 19.684 | 65.899% | 1190 RPM | 28.0 dB(A) | 0.893 |
| 12.084V | 5.042V | 3.332V | 5.068V | 29.870 | 115.12V | ||||
| 2 | 2.444A | 0.990A | 0.990A | 0.392A | 39.824 | 78.949% | 1220 RPM | 28.5 dB(A) | 0.964 |
| 12.090V | 5.042V | 3.331V | 5.065V | 50.443 | 115.11V | ||||
| 3 | 3.676A | 1.477A | 1.499A | 5.060A | 59.864 | 82.695% | 1230 RPM | 29.2 dB(A) | 0.980 |
| 12.089V | 5.040V | 3.330V | 5.060V | 72.391 | 115.11V | ||||
| 4 | 4.899A | 1.986A | 1.981A | 0.789A | 79.804 | 85.551% | 1240 RPM | 29.6 dB(A) | 0.987 |
| 12.087V | 5.039V | 3.328V | 5.057V | 93.282 | 115.11V |
The fan spins at high speeds, even under very light loads. In the first test, we'd like to see closer to 70% (or better) efficiency.
5VSB Efficiency
The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher with 100mA of load, 60 percent or higher with 250mA of load, and 70 percent or higher with 1A or more of load.
We take four measurements: one each at 100, 250, and 1000mA, and one with the full load the 5VSB rail can handle.
| Test # | 5VSB | DC/AC (Watts) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.102A | 0.514 | 77.879% | 0.076 |
| 5.070V | 0.660 | 115.09V | ||
| 2 | 0.252A | 1.275 | 80.696% | 0.163 |
| 5.068V | 1.580 | 115.08V | ||
| 3 | 1.002A | 5.068 | 81.335% | 0.350 |
| 5.057V | 6.231 | 115.08V | ||
| 4 | 3.002A | 15.093 | 79.253% | 0.449 |
| 5.029V | 19.044 | 115.08V |
The 5VSB rail is highly efficient. As far back as we can remember, all of the Corsair PSUs we've tested fare well in this discipline.
Power Consumption In Idle And Standby
In the table below, 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).
| Mode | 12V | 5V | 3.3V | 5VSB | Watts | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.094V | 5.042V | 3.331V | 5.071V | 7.715 | 0.470 |
| 115.1V | ||||||
| Standby | 0.036 | 0.004 | ||||
| 115.1V |
Vampire power is very low, facilitating high efficiency on the 5VSB rail (especially under light loads).
Fan RPM, Delta Temperature, And Output Noise
Our mixed noise testing is described in detail here.
Our first chart illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 37°C (98.6°F) to 47°C (116.6°F) ambient temperature.
The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a hemi-anechoic chamber. Background noise inside the chamber was below 16.6 dB(A) during testing. It's actually quite a bit lower, but our sound meter's mic is at its limit there. The ambient temperature was between 37°C (98.6°F) and 47°C (116.6°F).
The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 30°C (86°F) to 32°C (89.6°F).
Under normal temperatures, the PSU's fan doesn't make much noise until ~450W load. Even with 100W more, it stays below 31 dB(A). And in a worst-case scenario it doesn't exceed 34 dB(A). The fan profile is optimized for ~30°C ambient, though. Anywhere above 35-36°C, it starts to get really aggressive.
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