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 Rigol DS2072A oscilloscope kindly sponsored by Batronix, a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, two Fluke multimeters (models 289 and 175), 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 three more oscilloscopes (Rigol VS5042, Stingray DS1M12, and a second Picoscope 3424), and a Class 1 Bruel & Kj?r 2250-L G4 Sound Analyzer which is equipped with a type 4189 microphone that features a 16.6 -140 dBA-weighted dynamic range. You will find more details about our equipment and the review methodology we follow in this article. We also conduct all of our tests at 40°C-45°C ambient to simulate the environment seen inside a typical system with a higher accuracy, 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 specification 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.



The bulk caps have enough capacity to easily reach the 16 ms the ATX spec sets.

Inrush Current

Inrush current or switch-on surge refers to the maximum, instantaneous input current drawn by an electrical device when it is 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.



Inrush current was the highest we have ever recorded because of the large APFC caps used.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the DQ1250's efficiency. The applied load was equal to (approximately) 10%-110% of the maximum load the PSU can handle, in 10% increments.

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 can handle while the load on the minor rails was minimal.

For a high capacity PSU with Platinum efficiency, voltage regulation was pretty tight on all rails as all major rails stayed within 2%. The unit also easily delivered more than its full power at high operational temperatures that reached 46.5°C inside our hot-box. CWT obviously wasn't joking when it said this unit to deliver its full power continuously at up to 50°C. The cooling fan also never spun at full speed with a full load at 46°C as its fan-control circuit kept it at around 72% of its RPM, which kept noise output below 50 dBA in even our 110% load test. Finally, Efficiency at 20% load was only slightly below 90% and rose to easily surpassed 93% with 40%-70% load. Efficiency even hit 92% at full load, which shows just how much potential this high-end platform packs.

This is, generally speaking, a great PSU for you if you need lots of power and value a silently operating system at low loads. CWT did a great job with the platform, and its high efficiency allows the fan to rotate at low speeds.