6 - Testing
Load testing the PSU
Testing A PSU in theory it's not that difficult, stressing a 950 Watt PSU, now that's a little different.
Fact is that we do not have the gear in house to be able to stress this PSU to it's full capacity. We can connect everything we want, add more devices and overclock, but even then we'd normally peak at 500-550 Watts. But hey, as always let's try that out and see what happens.
So here's what we did. We took:
- eVGA Force 680i SLI mainboard (consumes heaps of current)
- Core 2 Quad Q6600 Processor (overclocked to 3 GHz)
- 2x GeForce 8800 GTX cards setup in SLI (624c - 1147m)
So to stress a little more we overclocked the CPU cores towards 3.0 GHz, had the DDR2 memory running at 1147 MHz and the two GeForce 8800 GTX cards toward 625 MHz on the core and 2100 MHz for its memory.
For the test we used a combo of X3: the reunion, 3DMark 06 . It's really nasty on graphics cards; it makes them sweat. We recently I added Call of Duty 4 as it's also multi-core threading.
Where we could we enabled 8xAA and 16xAF to make sure the graphics cards were working hard. The balance of these settings also ensures me that that the CPU is utilized as much as can be. Now at this point I realized that we're stressing the PSU slightly. So I added fan's, some extra lighting, water-cooling.
The 5 volts rail monitored
We monitored the primary voltages in both IDLE and LOAD (fully utilized) modes. 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.
Now look at the chart, the two lines show both the idle or Load state of a specific voltage rail, the yellow one the lowest voltage dip measured, the orange one the highest fluctuation. A 5% fluctuation is perfectly acceptable and falls with design specification, so 12 Volts should remain between 11.4 - 12.6 volts. The PSU when utilized stays away from that though all 12V rails where showing 12.37 volts in idle. A teeny bit on the high side. But other than that, there's no fluctuation when you compare the upper and lower voltage distribution.
The Power Supply is stable, did we expect any less ? 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.
