Efficiency

Using the efficiency results from the previous page, we plotted a chart showing the efficiency of the Twins 500 W at low loads and at loads equal to 20%-100% of the PSU's maximum-rated load.



Combining two PSUs isn't the best way to increase efficiency. On the contrary, at light and moderate loads, efficiency takes a big hit. Only when both power modules work at a typical load (at around 40%-50% of the maximum-rated-capacity) is there an efficiency advantage, which is why the Twins 500 W is very close to its efficiency peak at full load (the typical load for its power modules). Compared to normal PSUs with a similar capacity, the Twins 500 W stays far behind, especially at light loads.

Efficiency at Low Loads

We measured the efficiency of the Twins 500 W at loads much lower than 20% of its maximum-rated load (the lowest load the 80 Plus Standard measures) in these next tests. The loads we dialed were 40 W, 60 W, 80 W, and 100 W (for PSUs with a capacity over 500 W). This is important for settings where the PC is in idle mode with Power Saving turned on.


The 80% mark was only cracked in the last load test. Poor results here.

FSP Guardian Screenshots

You'll find screenshots of FSP's Guardian software below, which we captured with the PSU at light loads:

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible and recommends 50% or higher efficiency with 100 mA of load, 60% or higher with 250 mA of load, and 70% or higher with 1 A or more of load.

We will take four measurements: one at 100, 250, and 1000 mA, each, and one with the full load the 5VSB rail can handle.


Both 5VSB modules work in parallel, which totally cripples efficiency, with efficiency under light loads taking the largest hit. We don't remember ever seeing such a low efficiency reading on this rail before.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and voltage values of all rails (except -12V) when the PSU is in idle mode (powered on but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load at 5VSB).


The ErP Lot 6 2013 and even ErP Lot 6 2010 directives are out of reach since this unit consumes more than 2.5 W vampire power!

Fan RPM, Delta Temperature & Output Noise

The cooling fan's speed (RPMs) and the delta difference between input and output temperature are illustrated in the following chart. The following results were obtained at 37 °C - 45 °C ambient.



A chart that shows the cooling fan's speed (RPMs) and output noise follows. We measure the fan's noise from one meter away, inside a small custom-made anechoic chamber whose internals are completely covered in specialized soundproofing material (Be Quiet! Noise Absorber Kit). Background noise inside the anechoic chamber was below 20 dBA during testing, and the results were obtained with the PSU operating at 37 °C - 45 °C ambient.



The following graphs illustrate the fan's output noise and speed throughout the entire operating range of the PSU. The same conditions of the above graph apply to our measurements, but the ambient temperature was in-between 30 °C and 32 °C.





When the minor rails are pushed, the fan's profile goes crazy with even the lowest possible load at +12V. This is clearly a problem, and FSP should fix it as soon as possible!