OCZ ZS series 650W power supply review - Load testing the PSU

Load testing the PSU

Testing a power supple these days always is a bit of a challenge at hand. I mean without professional load testers it's pretty hard to stress a power supply of this class and actually measure its behavior.

Our first check is with a simple cheapo power supply tester, we monitor voltages quickly and check if all rails are working. All good here.

So for our load test here's what we did. We emulate real world usage. We take an Intel P55 based Quad SLI compatible motherboard, armed it with a GeForce GTX 590 card (has two GPUs per card).

We combined the P55 motherboard with a Core i7 870 processor overclocked to 3.8 GHz. The system, well have a look:

These are the components used:

• eVGA P55 Classified SLI motherboard (has high power consumption and an NF200 chip)
• Core i7 870 (overclocked to 3800 GHz) 20x190 BLCK at 1.4 Volts
• 1x GeForce GTX 590 primary (2 GPUs)
• 4 GB Memory DDR3 @ 1520 MHz
• SDD x1

Now with a setup like this, many years ago we'd reach 500~550 Watts power consumption as maximum. But with power supplies getting more and more efficient these days, even that proves to be a very hard task to accomplish.

So above our graphics card setup. Now on the software side of things it is time to give the PC a decent beating. Remember our focus remains PSU efficiency. At 50% load it should be the most efficient (~85%), that's under a 325W load.

We now take some other power supplies: 

• The Tagan BZ PSU is dating from 2008, that was a close to 80% efficient product. We suspect roughly 75% though.
• The 2nd generation BFG 1200W EX was rated March 2009, here's where efficiency started to matter and it was rated roughly 80%~84 efficient.
• The EnermaX  Platimax is rated at 94% efficiency, the platinum certification requires it to be 92% efficient at 50% load.
• The OCZ ZS 650W should be 85% efficient at 50% load.

We expected a little better efficiency for a Bronze certified PSU, then again we are stressing it more at the end of it's spectrum compared to say a kilowatt PSU. 50% load is the most efficient and the actual basis for 80+ certification, and we stress it with roughly 75% load in the game test.

Powered off all PSUs consume roughly 1-2 Watt. With the computer powered on and in absolute IDLE we can notice interesting differences.

In suspend to RAM or hybrid power mode the PSU kicks in nicely, we see roughly 1~2 Watt power consumption.