Efficiency

Using the efficiency results from the previous page, we plotted a chart to show the efficiency of the ST65F-G at low loads and at loads equal to 20-110% of the PSU's maximum-rated load.



At low loads, efficiency is close to other tested Gold units of similar capacity. About the same applies to normal loads, with the PSU almost scoring a 90% efficiency reading.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the ST65F-G at loads much lower than 20% of its maximum-rated load (the lowest load that the 80 Plus Standard measures). The loads that we dialed were 40, 60, 80, and 100 W (for PSUs with over 500 W of capacity). This is important for settings where the PC is in idle mode with power saving turned on.


In three out of the four tests we ran during this test session, efficiency was way above the 80% mark. Even a 40 W load yielded a 77.6% reading, which is quite good for the efficiency rating and the capacity of the unit.

5VSB Efficiency

The ATX spec states that the 5VSB standby supply's 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 that the 5VSB rail can handle.


The 5VSB rail isn't so efficient and fails to meet ATX spec recommendations on two tests. Even with a full load, it failed to register a reading over 75%. We expected more from this rail, and Enhance should upgrade its circuit—making it a little stronger and increasing its efficiency.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the 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).


As is the case for most units we test lately, this one is ErP Lot 6 2013 compliant as well, which translates into a reduced carbon footprint and a greener environment—something we should all propagate.

Fan RPM, Delta Temperature and 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 39-45°C ambient.



Although Silverstone states that the fan's maximum speed is restricted to about 1500 RPM, we measured close to 1800 RPM. They apparently took measurements at 40°C maximum ambient, not at the 45°C we conduct our tests in.

A chart that shows the cooling fan's speed (RPMs) and the output noise follows. We measure the fan's noise from 1 meter away—inside a small custom-made anechoic chamber with internals that are completely covered in specialized soundproofing material (Be Quiet! Noise Absorber Kit). Background noise inside the anechoic chamber was below 30 dBA during testing, and the results were obtained with the PSU operating at 39-45°C ambient.



The following graph illustrates the fan's output noise throughout the entire operating range of the PSU. The same conditions as for the above graph apply to our measurements, but the ambient in this case was between 28 and 32°C.



As you can see, the fan speed profile is normal and provides a quiet enough operation at normal ambient temperatures.