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.



The registered hold-up time was ridiculously low. OCZ/Sirtec should comply with the ATX specifications and make sure the 16 ms minimum is met, but they obviously preferred lowering production cost by using a smaller bulk cap instead.

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 they are turned on, the better.



Inrush current is low because of the small bulk cap, but we would highly prefer a larger bulk cap, although it would increase inrush current.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the FTY550W. 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 to reveal 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.


Voltage regulation is average on all rails except on 5VSB, where it is simply bad. Efficiency was close to what we expect from a Bronze unit of such a capacity, yet the only thing that fully pleased us was that the PSU managed to deliver its full power and even more at high ambient temperatures. The above table also nicely shows how very aggressive the fan profile is during our tests as the fan operated at full speed most of the time. The loose voltage regulation on the +12V rail even affected the fan's speed during the overload test since the latter is fed through the rail. The +12 V rail then skyrocketed during the CL1 test, which caused fan speed and noise output to increase significantly.

The results of the CL1 test, our Haswell compatibility test following Intel's guidelines, show that this unit doesn't meet the official Haswell compliance requirements. We should note that we don't expect a group regulated PSU to be able to meet these requirements and really wonder how OCZ came to the conclusion that its unit is Haswell ready.