What is the Best 600W+ PSU?

Seventeam ST-650PWL Review

Manufacturer: Seventeam
UK price (as reviewed): £56.79 (inc VAT)
US price (as reviewed): Unknown

Seventeam is once again attempting to establish a beachhead in the UK PSU market. The spearhead of the company’s attack is the ST-650PWL you see before you. As you can probably tell from the otherwise puzzling name, it’s rated as being able to supply up to 650W of DC power. As the ST-650PWL is the cheapest PSU in this group test, you’d be right not to expect much in the way of snazzy features; the PSU uses captive cabling and only the 24-pin ATX connector is braided.


The PSU uses the familiar approach of splitting its 12V power output over more than one 12V rail (in this case two); theoretically, this can improve stability and safety. The first of these two 26A rails supplies power to the 8-pin EPS12V and pair of 6+2-pin PCI-E connections, while the second takes care of the 24-pin ATX connection and all the SATA and Molex plugs.

At 50 per cent load, the ST-650PWL proved to be fully stable, outputting a steady 12.12V from its primary 12V rail and 3.26V and 4.8V from its 3.3V and 5V rails respectively. Its efficiency of 86 per cent at this load level was also reasonable for a budget model. Stepping up the Chroma machine we used for testing to the full 650W of which the PSU claims to be capable proved a sterner test for the ST-650PWL, but it completed it successfully.

All of its rails also remained within the ATX spec, even when under full load for an extended period of time. As expected, though, its efficiency dipped a little at full load, meaning that the PSU was only 83 per cent efficient when outputting its maximum rated wattage. Running the PSU at 100 per cent load revealed that the fan attached to the ST-650PWL is also a weak point of the unit, as it produced a particularly noticeable buzzing noise when it spun up.

Surprisingly for such a cheap PSU, the ST-650PWL revealed excellent holdup times on both its 12V and 5V rails, easily exceeding the 17ms holdup time recommended by the ATX spec. Its ripple result of 35.3mV was also reasonable, although a fair way behind the best result we saw. The ST-650PWL is surprisingly solid for such a cheap PSU but it’s obvious that it’s a budget model, thanks to its captive, unbraided cables.

The fact that it only has a pair of 6+2-pin PCI-E limits its appeal too. We recommend forking out the extra £15 or so for the Corsair Professional Series HX650, which has modular cables, is more efficient and has more PCI-E plugs.