Running the numbers
Our testing procedures can be found at this link.
Efficiency
| Load | 10pc | 25pc | 50pc | 75pc | 100pc |
|---|---|---|---|---|---|
| Efficiency | 78.4pc | 85.2pc | 88.1pc | 87.3pc | 86.0pc |
Efficiency is higher, read better, than that mandated by 80 PLUS' Bronze certification when evaluated from a 230V source. The supply pulls 425W from the mains to deliver a 50 per cent load of 375W to the Chroma test equipment, losing 50W in resistance and heat. Ramp it all the way up to a desired 750W - constituted by 12V load, in the main - and the supply needs 872W from the mains. Providing some context, a Platinum-rated PSU of the same capacity would need no more than 824W for the same full-load draw. Overall, considered with respect to its class, efficiency is decent for a £65 supply.
Regulation
In terms of regulation, we're looking at just how well the supply is able to hold to the various lines. The ATX spec. has a +/- 5 per cent leeway on all but the -12V line.
| Line/Load | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | +1.5pc | +0.6pc | +1.4pc |
| 50 per cent | -0.3pc | -0.8pc | +0.6pc |
| 100 per cent | -2.2pc | -1.9pc | -1.3pc |
Genuinely premium supplies can hit each of the preset loads by wavering less than one per cent away from ideal voltage regulation. The GreenMe 750W isn't as good, understandably so given its price, but remains well within the ATX specification.
Regulation - cross-load
How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 60A on the 12V rails, and 1A on the 3.3V and 5V rails. This can actually be somewhat typical for a system heavy on graphics and CPU power. In the second, we've turned the tables and gone for 12A on both the 3.3V and 5V rails - highly unlikely in a real-world environment - and just 2A on the 12V - even more unlikely!
| Line/Load | 3.3V | 5V | 12V |
|---|---|---|---|
| Cross-load 12V focus | +1.3pc | +1.1pc | -1.0pc |
| Cross-load 3.3V/5V focus | -1.9pc | -2.2pc | +1.8pc |
Hammering one part of the PSU power delivery while using just a small portion of the other can throw cheaper supplies of out kilter. Pushing and pulling the voltage and lines does cause the regulation to suffer a touch. But again, it's nothing that we'd worry about.
Ripple
| Line/Load (mv - p-p max) | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | 10mV | 10mV | 15mV |
| 50 per cent | 15mV | 10mV | 45mV |
| 100 per cent | 20mV | 18mV | 80mV |
The ATX v2.2 spec states that the maximum permissible ripple is 120mV for the 12V line and 50mV for others.
PSUs convert AC power into DC, but doing so requires the AC waveform to be suppressed. What we're really testing here is the quality of the supply's rectifier and any smoothing capacitors in getting rid of this unwanted up-and-down ripple. The standout figures are for 50 and 100 per cent load on the 12V line. The numbers are perfectly within ATX specification but cannot get close to the 30-50mV standard set by a number of Gold and Platinum supplies. Considering it properly, with respect to price vs. capacity, the In Win GreenMe 750W meets and exceeds common standards though its 12V ripple does start to become noticeable at full load.
Temps and noise
| Temperatures | Intake | Exhaust |
|---|---|---|
| 10 per cent | 27°C | 34°C |
| 50 per cent | 32°C | 37°C |
| 100 per cent | 37°C | 45°C |
High efficiency ratings tend to go hand-in-hand with low-ish temps; there's not a great deal of heat being created by the PSU. The supply's fan is active at all times, unlike some of the competition, but it's not noticeable at loads below 50 per cent. Increase the load to around 75 per cent and the fan spins up to around 1,250RPM. We'd term the noise just above average for a supply of this class.
