The results
Our testing procedures can be found at this link. In the interests of full disclosure, we can only tap into four of the six rails on the supply. This is still enough to hit the total capacity of 1,200W without tripping any overprotection settings. Ambient temperature is 25°C, well below the 50°C the supply is rated at.
Efficiency
| Load | 10pc | 25pc | 50pc | 75pc | 100pc |
|---|---|---|---|---|---|
| Efficiency | 84.9pc | 91.8pc | 92.7pc | 91.6 | 90.3pc |
The 10pc load equates to a significant 120W of load. Consider that an Intel Core i5 2500K PC with a premium Radeon HD 7950 going full chat only consumes 200W or so and you quickly realise just how much power the Platimax 1,200W is capable of delivering.
Around 85 percent efficiency is actually very good for 10pc load, which is probably the kind of wattage a high-powered system will idle at.
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 | +2.0pc | +2.1pc |
| 50 per cent | +0.2pc | +1.4pc | +0.3pc |
| 100 per cent | -1.3pc | 0pc | -1.8pc |
The EPM1200EWT provides a little more than needed on the rails until we hit around 50 percent on each main line. After this the regulation falls into negative territory, although it remains well within ATX specifications. Hammer it and the 12V line falls to around 11.8V, we observed. Regulation could, and should, be better on Enermax's top-of-the-line supply, we suppose.
Regulation - cross-load
How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 100A on the 12V rails, and 1A on the 3.3V and 5V rails. This can actually be somewhat typical for a system supremely heavy on graphics and CPU power. In the second, we've turned the tables and gone for 15A 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 | -1.0pc | +0.2pc | -1.9pc |
| Cross-load 3.3V/5V focus | -1.4pc | +0.3pc | +0.4pc |
Numbers fall within specification and there's little to be worried about. We'd like them closer to the ideal, but even pushing and pulling the supply's power-delivery system can't throw it off.
Ripple
| Line/Load (mv - p-p max) | 3.3V | 5V | 12V |
|---|---|---|---|
| 10 per cent | 15mV | 15mV | 10mV |
| 50 per cent | 20mV | 20mV | 20mV |
| 100 per cent | 25mV | 30mV | 25mV |
The ATX v2.2 spec states that the maximum permissible ripple is 120mV for the 12V line and 50mV for others.
Ripple is very good on the 12V rail, which is the one you'll most likely be beating on. Do remember that even 25mV is way, way below (read better) than ATX specs.
Temps
| Temperatures | Intake | Exhaust |
|---|---|---|
| 10 per cent | 28°C | 32°C |
| 50 per cent | 30°C | 36°C |
| 100 per cent | 35°C | 44°C |
The supply is barely tickled at a 10 per cent load and doesn't become overly warm at either 50 per cent or maximum continuous load.
We'd normally report the noise rating, but such is the din produced by the Chroma machine - ears are still ringing - that doing so would be completely pointless. What we can say is that the supply is practically silent at low-to-medium loads. It does become noticeable when nearing 100 per cent, but the noise produced by, say, three Radeon HD 7970s or GTX 580s would mask it completely.
Results recap
Plenty of power is delivered smoothly at all wattage levels. In particular, the ripple, of lack thereof, is good on the critical 12V line.
