Thinking behind a top-quality supply
Though often homogeneous on the outside, power-supply units (PSUs) are amongst the most diverse PC products when evaluated from the inside. There's no absolutely right way to manufacture a supply, and each company that plies its trade in this segment has a different take on just how to construct the 'best' PSU.
Perhaps better known for its heritage in graphics, XFX has been steadily encroaching into the world of PSUs. Its current line-up is refreshingly simple, made up of Pro and Classic lines. Most of the attention in 2011 has been placed on the Pro series, with no less than 10 supplies available. Sitting right at the top of the tree is the ProSeries 1,250W PSU, which is based on a high-end offering originally manufactured by Seasonic.
A distinct lack of any pre-plumbed wires means it's a fully-modular supply - all the cables are provided in the package - and thus you only connect what you really need.
XFX also touts a hybrid fan-speed mode, where the supply's 135mm fan automatically switches off - it is always on at boot, however - if the load is below 20 per cent (250W) and the internal temperature below 25°C. Cross any of these barriers and it jumps to 'quiet' mode, applicable right up to 50 per cent load, where it spins in a near-silent manner. Bear in mind that 50 per cent load on this PSU is a very healthy 625W. In short, XFX is claiming this to be a very quiet PSU for most mid-load scenarios.
Also available as a 1,000W PSU, the ProSeries is an 80 PLUS 'Gold'-certified supply, which means it must be at least 92 per cent efficient from a 50 per cent load on a 230V supply. Helping keep the efficiency rating high is what XFX terms 'SolidLink' technology. Look at the above-right picture and you'll notice the connectors are joined to the board not by the usual gaggle of wires, but through solid (and fewer) pins. We're sceptical of just much cable-loss is removed by such an approach; XFX quotes efficiency improvements of a few watts, and this may be enough to jump an 80-PLUS class.
The Pro 1,250W measures 190mm (d) by 150mm (w) x 86mm (h) and its dimensions are considered average for a supply of this throughput. Users looking at such a PSU will likely have full-tower chassis and adequate room to house it in. The supply feels well-built and supremely sturdy, with no squeaks or rattles, though removing the front portion by the modular connectors reveals that to be rather flimsy, though we'd imagine most users wouldn't need to do so. XFX backs it up with a five-year limited warranty, matching what's on offer from the rest of the industry.
We like the fact that the 1,250W of juice on tap is guaranteed at an ambient (in-case) temperature 50°C, which is a must when one considers just how hot a chassis with, say, four GeForce GTX 580s can become. Understanding that any high-wattage PSU is likely to be loaded with heavy bombardment on the 12V lines - CPUs and graphics-cards chew on this - the Pro 1,250W uses a 12V single-rail architecture. We can long-argue whether it's better to have a single or multiple rails, but opting for the former, as XFX has done, makes everything simple: you know how much power is available on the line and needn't worry about overloading a particular rail - 12V3, for example.
Indeed, here's how the Pro 1,250W's wattage topography maps out:
|Amps/watts and voltage||3.3V||5V||12V||-12V||+5VSB|
|Maximum rating (combined)||150W||1,248W||6W||15W|
|Maximum rating continuous||1,250W|
Blasting the 12V line is what the Pro is made for, clearly. Playing with such high wattages brings copious amounts of protection into play. The supply will switch off if the total power is 135 per cent of the maximum continuous and over-voltage protection kicks in at between 10-20 per cent over the 3.3V, 5V and 12V lines. Keeping it all usable under extreme load, there's also over-current, over-temperature and short-circuit protection, too. On first glance, the Pro 1,250W has all the important bases covered.