Corsair HX750i PSU review - Load testing the PSU

Load testing the PSU

Testing a power supply these days is always 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. A perfect score.

The test setup

So for our load test here's what we did. We emulate real world usage in this stage. We take an old energy hungry Intel P55 based Quad SLI compatible motherboard, armed it with GeForce GTX 590 cards (each card has two GPUs). We combined the P55 motherboard with a Core i7 870 processor overclocked to 3.8 GHz. That will drain the system alright. The system... well have a look:

These are the components used:

• P55 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
• OCZ Vertex 2 SDD x1

Now, with a setup like this, a couple of years ago we'd have reached 500~550 Watts power consumption as maximum. But with power supplies getting so incredibly 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 on PSU efficiency. We now take some other power supplies and start testing with one GeForce GTX 590 first: 

Looking at efficiency is actually a simple thing to do, we apply the same load on several power supplies, from old to new. We look at the powered off status, Windows IDLE status, productivity mode (we stress the CPUs) and during gaming. The lower the Wattage, the more efficient. The IDLE power consumption is average to normal.

The best indicator for good efficient power consumption is by looking at the game test. As you can see the Corsair HX750i consumes power according to the platinum norm set by other Platinum power supplies. Powered off most PSUs consumes just over 0 Watt. But let's zoom in at load testing. 

When we focus solely on CPU productivity mode load for a second we see that the PSU draws 266W from the wall socket. As you can see, the efficiency is smack in the upper class of efficiency. For this kind of certified PSU, that's pretty spot on.

When we focus solely on gaming load, we see that the PSU draws 451 W from the wall socket. Again, these are your average results. At ~375W power draw this 750 Watt PSU should be the the most efficient -- as at 50% load a PSU is usually the most efficient. The efficiency values even slightly below 50% load actually remains roughly at Platinum level efficiency albeit offering best in class numbers. That actually is very nice to see.