OCZ EliteXStream 1000 W Power Supply Review

Load Tests

We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.

We tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.

If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.

+12V1 and +12V2 are the two independent +12V inputs  from our load tester and on this case they were connected to the same rail from the power supply, as OCZ EliteXStream 1000 W features a single rail design.  The configuration below is exactly the same we used on our tests with other 1,000 W power supplies, like OCZ ProXStream 1000 W and Corsair HX1000W.

Updated 06/25/2009: We re-tested this power supply using our new GWInsteak GPM-8212 power meter, which is a precision instrument and provides accuracy of 0.2% and thus presenting the correct readings for AC power and efficiency (results marked as "2" on the table above; results marked as "1" were measured with our previous power meter from Brand Electronics, which isn’t so precise as you can see). We also added the numbers for AC voltage during our tests, an important number as efficiency is directly proportional to AC voltage (the higher AC voltage is, the higher efficiency is). Also, manufacturers usually announce efficiency at 230 V, which usually inflates efficiency numbers. We added power factor (PF) numbers as well. These numbers measure the efficiency of the power supply active PFC circuit. This number should be as close to 1 as possible and the active PFC circuit from this unit is outstanding, as it was able to maintain power factor at 0.99 for all loads.

This power supply can really deliver 1,000 W at 50° C with an amazingly low noise level. Ripple and noise were always below 10 mV at +5 V outputs, where the maximum admissible value is 50 mV (peak-to-peak values)!  Pulling 1,000 W from this power supply noise level on +12 V and +3.3 V outputs were not even half of the maximum admissible (which is 120 mV for the +12 V output and 50 mV for the +5 V output).

Voltages were very stable all the time, although +3.3 V and +5 V outputs dropped a little bit during test number five (power supply delivering 1,000 W), but still inside the 5% tolerance set by the ATX/EPS12V standard.

Even -12 V was incredible stable and with very low ripple. Usually the -12 V output oscillates like crazy, because manufacturers use cheap solutions for its rectification, filtering and regulation. Since this power supply used a voltage regulator integrated circuit to handle this output it achieve excellent results on this output. The maximum noise level we’ve seen for it was 13.8 mV when the power supply was delivering 1,000 W; on Corsair HX1000W, for example, noise level at -12 V was at 62 mV when it was delivering the same amount of power.

You will get a high efficiency with this power supply if you pull up to 60% of its labeled capacity (600 W): between 83.5% and 85%. With 80% load (800 W) efficiency dropped to 81.5%, still above 80%. But when we pulled around 1,000 W efficiency dropped below the 80% mark: 78.2%. This is not really a problem, as high-wattage power supplies are targeted to users that what to run them at half of their labeled capacity in order to achieve the best efficiency possible (click here to learn more about this question). You will never be able to pull anywhere close to 1,000 W with a personal computer.

Below you can see noise level when we were pulling 995 W (test number five) from this power supply. Just to remember, the maximum allowed for the +12 V outputs is 120 mV peak-to-peak and the maximum allowed for the +5 V and +3.3 V outputs is 50 mV peak-to-peak.

Figure 16: Noise level at +12V1 input from our load tester with the reviewed unit delivering 995 W (47.4 mV).

Figure 17: Noise level at +12V2 input from our load tester with the reviewed unit delivering 995 W (41.2 mV).

Figure 18: Noise level at +5 V input from our load tester with the reviewed unit delivering 995 W (9.8 mV).

Figure 19: Noise level at +3.3 V input from our load tester with the reviewed unit delivering 995 W (23.4 mV).

Unfortunately we couldn’t test if this power supply could deliver more than 1,000 W due to a limitation in our equipment. On test number five (1,000 W) we were already pulling the maximum amount of current our equipment is capable of pulling from its two +12 V inputs (33 A or 396 W each). Thus we couldn’t pull more than 1,000 W the way we wanted. Of course we could keep the +12 V inputs at 33 A and increase current at +5 V and +3.3 V, but that is not the configuration we wanted, as we always want to pull as much as we can from the +12 V outputs from the power supply, as today that is where consumption is concentrated (video cards and CPUs are fed by the power supply +12 V outputs through the video card auxiliary cables and EPS12V/ATX12V, respectively).

For the same reason we couldn’t test the power supply over current protection (OCP), since EliteXStream 1000 W +12 V rail has a limit of 80 A but we could pull only 66 A.