FSP Epsilon 700w ATX PSU

Load Testing

In order for the results from all current and future PSU reviews to remain fair and comparable, Overclock3D uses a custom built Power Supply load stress tester.

The tester is capable of placing loads on the following rails:

 

+3.3v – 20a Load
+5.0v – 20a Load
+12v1 – 10a Load
+12v2 – 10a Load
+12v3 – 10a Load
+12v4 – 10a Load
(or 10-40a on a single +12v rail)

The results are collected from a Mastech MAS-345 Multimeter which logs its readings via RS232 to a PC.

The results given out by the Epsilon were extremely strange. Rather than the voltage on the rails dropping under load as expected, the voltages on the 3.3v and 12v rails actually increased by quite a worrying amount.

I don’t have any real explanation for these results other than the possibility that the Epsilon 700w has some unusual crossloading requirements, or that the power supply has tried to compensate for the load placed on the rails by increasing the voltage (too far).

Either way, an increase in voltage also means a decrease in amperage, which means that the Epsilon may be falling short of its rated output.

Just in case there was an incompatibility between our power supply tester and the Epsilon, we have also tried the unit in our test machine which comprises of the following components: 7900GT, P4 Prescott @ 4.1ghz, 2gb Ram, Laing D5 Pump. The results can be seen below:

Rail
Idle Voltage
Load Voltage +3.3v 3.29 3.27 +5v 5.08 5.06 +12v1 12.24 12.21 +12v2 12.28 11.91 +12v3 12.25 11.98 +12v4 12.23 12.16

When plugged into a high-end PC, the Epsilon gives voltage readings much more like what we’d be expecting. All voltages remained within ATX specification, and despite the +12v rails dipping by around 0.3v, never fell low enough to cause any problems.

Efficiency Testing

Efficiency tests are performed by measuring the wattage consumed by the power supply at the mains against the power (in watts) consumed by the OC3D power supply stress tester.

The results may not be as accurate as those produced by professional testing equipment, but will certainly come in handy when comparing several power supplies against each other.

The Epsilon 700w was placed under a load of 646 watts. This counts for a total of 92% of the power supplies rated output. At this load, the power supply required 723 watts from the mains to produce the 646 watts required by our custom made power supply tester.

Therefore the efficiency of this power supply can be found by a simple equation: (646 / 723) * 100, which works out to be an efficiency rating of 89.3%

With a load of 646w which is very close to the maximum output of this power supply I was pleasantly surprised by the efficiency, which is in line with the figures given by FSP for this unit.

 

Noise Testing

As mentioned earlier in the review, the Epsilon 700w makes use of a 2500rpm, 38.3dB fan manufactured by Protechnic Electrics, which pushes 80cfm when running at 12v.

This many not seem the kind of fan you’d associate with a quiet running PC. Thankfully FSP limit the speed of the fan based on the PSU load to counteract this.

In idle situations, the power supply is barely audible at 1 metre away. I’d estimate the noise output at idle to be around 20dBA. However under heavy load the Epsilon increases the speed of the fan substantially, making the unit clearly audible for 1 metre away. I would estimate the noise output under load to be around 28-30dBA.