Test Setup

All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. We also used a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, a Fluke 175 multimeter, and a Yokogawa WT210 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. Finally, we had at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12, a second Picoscope 3424), and a CEM DT-8852 sound level meter. You will find more details about our equipment and the review methodology we follow in this article. Finally, we conduct all of our tests at 40°C-45°C ambient in order to simulate with higher accuracy the environment seen inside a typical system, with 40°C-45°C being derived from a standard ambient assumption of 23°C and 17°C-22°C being added for the typical temperature rise within a system.

Primary Rails Voltage Regulation

The following charts show the voltage values of the main rails, recorded over a range of 60 W to the maximum specified load, and the deviation (in percent) for the same load range.

5VSB Regulation

The following chart shows how the 5VSB rail deals with the load we throw at it.

Hold-up Time

Hold-up time is a very important PSU characteristic and represents the amount of time, usually measured in milliseconds, a PSU can maintain output regulations as defined by the ATX spec without input power. In other words, it is the amount of time the system can continue to run without shutting down or rebooting during a power interruption. The ATX spec sets the minimum hold-up time to 16 ms with the maximum continuous output load. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.



Regardless of the pretty large bulk cap, the PSU failed to pass the hold-up test. It only achieved 12.8 ms. However, it didn't register a huge fail since it only failed by 3.2 ms, while we have seen other units score way lower hold-up times.

Inrush Current

Inrush current or switch-on surge refers to the maximum, instantaneous input-current drawn by an electrical device when first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches, relays and bridge rectifiers; as a result, the lower the inrush current of a PSU right as it is turned on, the better.



The different platform this PSU utilizes and the large bulk cap led to the above result. As you can see, the smaller RM model registered a higher inrush current than the two larger RM units.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the RM650. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100%, and 110% of the maximum load the PSU can handle. We conducted two additional tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 0.10 A. This test reveals whether the PSU is Haswell ready or not. In the second test, we dialed the maximum load the +12V rail could handle while the load on the minor rails was minimal.


Voltage regulation on the +12V rail was pretty good, and close enough to 2% on the minor rails; not the best voltage regulation we have ever seen, but good enough overall for the category. Also, contrary to the RM750/850 units where the fan starts to spin really late, allowing for excess temperatures internally, the RM650 has a better fan profile that engages the fan earlier, which doesn't stress heat-sensitive components as much. During the first two of the above load tests, the PSU operated in fanless mode, and the fan only started to spin at initially increased speed to move hot air out of the PSU's enclosure around the middle of the 50% load test. Afterward, it slowed down and increased its RPM only after the 80% test, where things started to get hotter. As you will notice, the fan's RPM was then kept low at even full speed, and the same applied to its output noise.

Efficiency was high enough for this platform, though it doesn't exploit any exotic topologies or components, peaking at 92.2% with 40% of the maximum-rated-capacity load. The RM650 is then, all in all, efficient; it may not be up to Platinum efficiency levels, but also costs way less while managing to perform rather well efficiency-wise. Our Crossload #1 test results will also show you that 5V performance wasn't affected significantly by the missing bridge we spotted on the modular PCB, which resulted in fewer 5V cables on the main ATX connector. Obviously not a major problem, we still don't understand how CWT could have missed it.

Corsair Link Screenshots

Several screenshots of the Corsair Link software, which we took during our test sessions, follow. The order of screenshots is the same as the order of tests in the above table (20% Load to Cross-load 2).