What is the Best 600W+ PSU?

Be Quiet! Dark Power Pro P9 650W

Manufacturer: Be Quiet!
UK price (as reviewed): £136.88 (inc VAT)
US price (as reviewed): Unknown

The Dark Power series resides at the top of Be Quiet!’s range of PSUs and is targeted at PC enthusiasts. As you’d expect, then, these PSUs carry a hefty feature list and a price to match - the Be Quiet! Dark Power Pro P9 650W is one of the most expensive PSUs on test. It’s worth noting, though, that while the PSU is designed by Be Quiet!, it’s actually manufactured by FSP.


On the face of it, you’re getting a lot of PSU for your money; the Dark Power Pro P9 650W is 200mm long, noticeably longer than any other PSU on test, despite providing a similar amount of power. This extra size enables Be Quiet! to add more features to the PSU and gives the components inside more room to breathe, but it could cause compatibility problems with smaller cases.

As you’d expect from a premium PSU, the P9 650W is modular, with only the 24-pin ATX cable permanently attached to the PSU. Attaching the cables needed to build a PC is a breeze, though, as the sockets for the tidily braided cables are clearly labelled, and use differently shaped connectors; it’s virtually impossible to wire up the PSU incorrectly.

There are plenty of cables from which to choose too, as the PSU provides six Molex connections, nine SATA connections and a single floppy plug. The P9 650W also provides four PCI-E connections, although only two of these are 6+2-pin. Meanwhile, next to the modular cable sockets is a small white switch that enables you to toggle between having four 12V rails and just one huge rail. Be Quiet! claims that this should be used when overclocking, but we’re dubious about how much of a difference it will make.

Whether you’ve set the PSU to provide its 12V power over one rail or four, it will still have a maximum claimed 12V output of 53A. This is complemented by the 3.3V and 5V rails, both of which are rated at 24A, and a 0.5A –12V rail and a 3A 5VSB rail. The P9 650W also proved to be 100 per cent stable during our testing, staying well within the ATX spec on each of its rails, even when running at full load for an extended period of time.

It was also pleasingly efficient at both half and full load, achieving 91 per cent and 90 per cent efficiency respectively. The PSU performed very well in our holdup tests too, as it was one of the few PSUs we tested that exceeded the recommended 17ms holdup time on both its 12V and 5V rails. There’s no denying that the P9 650W is a competent, PSU but it’s overshadowed by the better-connected and more powerful Antec High Current Pro HCP-750, which costs just a little more.