7 - Load Testing the PSU

As explained in the previous chapter, we monitored the primary voltages in both IDLE and LOAD (fully utilized) modes. Now we tap each rail one at a time. We noted down the lowest and highest value we see and that is the fluctuation. If a PSU is unstable we'd see much more fluctuation, differences and discrepancies which can result in system instability.

These results are then placed into the chart you can see below.

Now look at the chart, the two lines show both the idle or load state of a specific voltage rail, the blue one the lowest voltage dip measured, the red one the highest fluctuation. A 5% fluctuation is acceptable and falls with ATX design specification, so 12 Volts should remain between 11.4 - 12.6 volts.

I must applaud the industry as pretty much not one PSU in the last year was showing any discrepancy. It is good to see where we are right now.

Anyway, the BFG is showing just no fluctuation when you compare the upper and lower voltage distribution.

During the load test several times I felt (doing it manual with your hand is often practical) to see if the PSU was warm, it remained cold at all times. It feels like it's hardly doing anything at all.

Very notable is this;

With one 9800 GX2 yet with the system overclocked we noticed that wattage did not peak over 500 Watts where other PSU's in the past have shown higher peak loads. We reached 414 Watt with one GeForce 9800 GX2 - 2GB memory - QX9770 - NFORCE based and overclocked system.

This is the moment where I need to remind you about about power efficiency. This PSU's efficiency is really good and it's showing. We estimate between 80% and 85% efficiency which is on par with the specification.

Once we add the second GeForce 9800 GX2 and render the game with 4 logical GPU cores the system needs to work much harder. We actually 631 Watt which is ridiculous in today's green conscience world, obviously. But the the point here is, the PSU did the job perfectly fine. In fact it didn't even get slightly warm, meaning it can handle high-load really well.