Load Regulation, Hold-Up Time, And Inrush Current
To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units.
Primary Rails And 5VSB Load Regulation
Load Regulation testing is detailed here.
Our hold-up time tests are described in detail here.
The hold-up time we measured is very low. Normally it should be at least 17ms; in this case it dips under 10ms. The only redemption comes from the power-good signal dropping before the rails go out of spec. Still, Corsair should use a larger bulk cap to increase the CX750M's unit's hold-up time.
For details on our inrush current testing, please click here.
Inrush current registers on the high side, especially with 115V input. We would like to see readings under 50A.
Load Regulation And Efficiency Measurements
The first set of tests reveals the stability of the voltage rails and the CX750M's efficiency. The applied load equals (approximately) 10 to 110 percent of the PSU's maximum load in increments of 10 percentage points.
We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.1A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails.
|Test #||12V||5V||3.3V||5VSB||DC/AC (Watts)||Efficiency||Fan Speed||Fan Noise||Temps (In/Out)||PF/AC Volts|
|1||4.408A||1.983A||1.995A||0.991A||74.80||79.25%||760 RPM||25.2 dB(A)||37.29°C||0.982|
|2||9.866A||2.978A||3.003A||1.196A||149.78||84.82%||760 RPM||25.2 dB(A)||37.76°C||0.983|
|3||15.695A||3.486A||3.524A||1.400A||224.89||86.54%||760 RPM||25.2 dB(A)||38.92°C||0.990|
|4||21.541A||3.993A||4.020A||1.606A||299.80||87.05%||760 RPM||25.2 dB(A)||40.21°C||0.993|
|5||27.067A||4.998A||5.040A||1.814A||374.73||86.67%||970 RPM||32.3 dB(A)||41.86°C||0.995|
|6||32.609A||6.024A||6.064A||2.023A||449.74||86.00%||1180 RPM||38.1 dB(A)||42.66°C||0.996|
|7||38.182A||7.041A||7.095A||2.235A||524.66||85.06%||1375 RPM||42.3 dB(A)||43.41°C||0.997|
|8||43.770A||8.077A||8.133A||2.450A||599.65||83.92%||1610 RPM||45.2 dB(A)||44.58°C||0.997|
|9||49.834A||8.595A||8.673A||2.455A||674.71||82.51%||1705 RPM||46.8 dB(A)||44.85°C||0.997|
|10||55.643A||9.122A||9.190A||3.090A||749.63||81.17%||1925 RPM||49.2 dB(A)||45.82°C||0.997|
|11||62.072A||9.132A||9.207A||3.097A||824.44||79.71%||2070 RPM||50.9 dB(A)||46.07°C||0.998|
|CL1||0.100A||15.980A||15.986A||0.001A||132.23||78.92%||760 RPM||25.2 dB(A)||43.67°C||0.982|
|CL2||61.943A||1.001A||1.003A||1.002A||747.60||82.00%||1965 RPM||49.7 dB(A)||46.91°C||0.998|
Load regulation is decent, though not as good as the CX650M. The same goes for efficiency. It is obvious that this platform can't offer the same performance as the smaller CX-M models, and that's disappointing since we expected performance to go the other direction. To make matters worse, the 80 PLUS Bronze requirement of at least 82% efficiency under full load isn't met; this PSU barely passes 81% efficiency in that test. As usual, we have to concede that 80 PLUS conducts its measurements at a very low ambient temperature, whereas ours was a more realistic 46°C. It's natural to measure lower efficiency in warmer environments.
Output noise is pretty low up to around 40% load. Similar to the CX650M, though, Corsair's minimum fan speed is set pretty high. We think it should be closer to 500 RPM. Under higher loads and increased operating temperatures, the fan makes a lot more noise. Beyond 70% of the CX750M's maximum rated capacity, its fan is downright loud.