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 from 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.



Like its bigger sibling, this PSU, too, failed to pass the hold-up test. We are very disappointed when we see hold-up times that don't even exceed 10 ms.

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.



Although hold-up time was low, which indicates that larger bulk caps should be used, inrush current was pretty high, but thankfully not high enough to be worrisome.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the R3 800 W. 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 was great on all rails, with only 3.3V exceeding the 1% mark. This platform is able to deliver super-stable rails, as we already figured out in the R3 1000 W review. It is also very efficient as efficiency only dropped below 90% during our CL1 efficiency test, peaking at nearly 93% with 40% load. The temperature column also shows the fan engaging during the 20% load test and onward. It, since the ambient inside our box was already pretty high, had to engage to move heat out of the unit's internals. Some semi-passive units engage their fans very late, which puts a lot of stress on components like electrolytic capacitors, but this PSU thankfully didn't fall into that trap. We prefer a slowly rotating fan over a passive operation, and a user must have superman's hearing to be annoyed by the fan's output noise at such low speeds.