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Corsair RM850x (2018) PSU Review

Protection Features

Our protection features evaluation methodology is described in detail here.



12V: 90A (127.12%), 11.994V
5V: 33.2A (132.8%), 5.053V
3.3V: 34.1A (136.4%), 3.312V
5VSB: 5.4A (180%), 4.888V


1095.7W (128.9%)


✓ (180°C @ 12V board)


12V: ✓
5V: ✓
3.3V: ✓
5VSB: ✓
-12V: ✓


Proper Operation



Surge: MOV
Inrush: NTC Thermistor & Bypass Relay

The OCP and OPP triggering points are reasonable set, while the 5VSB rail is set rather high at 180% of its nominal output. Nonetheless, we don’t measure increased ripple and the voltage is within the ATX spec.

As expected the over temperature protection’s triggering point is set high, providing enough room for a prolonged passive operation. After all the +12V parts, which are stressed the most, are highly tolerant to increased temperatures. Finally, the power ok signal is accurate and there is short circuit protection on all rails.

DC Power Sequencing

According to Intel’s most recent Power Supply Design Guide (revision 1.4) the +12V and 5V voltages must be equal or greater than the 3.3V rail’s output at all times, during the power-up and normal operation. For our first measurement, we turn the unit off and switch it back on without any load in any of the rails.

In the second test, we set the PSU to standby mode, dial full load and start it afterwards. In the last test, while the power supply is completely switched off (we cut off the power or switch the supply off through its power switch), we dial full load before restoring power.


The results are perfect since in all cases the 3.3V rail’s voltage is lower compared to the rest two rails and the peaks are within the 20ms range that the ATX spec requires.

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