OCZ ModXStream Pro 500W PSU

Results

The voltages remained solid throughout our testing - even up to full load and the extended 30 minute stress test as well. Even the very slight dips with extremely heavy loading are well within ATX spec.

The active PFC was consistently quite high, although we have seen a few percent higher (95+) elsewhere, and the efficiency is pretty good at 84 to 85 percent at 50 to 100 percent load. At 20 percent load, efficiency drops off a bit at a nudge over 81 percent, so it's closer to the 80 Plus certification than 80 Plus Bronze. The difference between these two efficiencies at 100W (20 percent) load is only 6W, which will hardly break the bank; you'll likely pay more for better internal hardware anyway.

During testing we found that the fan was better when the PSU was on its side or with the fan facing downward, rather than having the fan pointing upward, pushing air down into it. Sat with fan grille upwards, the fan would gently go "GR-GR-GR-GR-GR-GR", although we have to say this noise was only noticeable up close.

With the unit sat on its side or with the fan facing downwards, the fan was practically silent at 50 to 75 percent load as it continued to revolve at a very low RPM. At full load the fan kicked up a notch, retaining this speed for the full 30 minute stress test, However, the fan was still very quiet and unobtrusive throughout.

We checked the temperatures internally during the stress test and found the maximum temp on the transformer was a very tolerable 55ºC, while most of the other internal temperatures ranged from a very cool 30 to 40ºC. This in spite of the basic heatsinks; it seems OCZ has made a sensible choice by not adding the unnecessary price of more extravagant cooling. The sides and modular connectors remained cool, and the base of the PSU and the exhaust air was acceptably warm.

Overall, we think OCZ has a great result here - the ModXStream Pro 500W ran reasonably cool, generally very quiet, and delivered solid efficiency and voltages.