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Load Tests

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

First 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 during our tests the +12V1 input was connected to both +12V1 rail and +12V2 rails and the +12V2 input was connected to the +12V2 rail.

Input Test 1 Test 2 Test 3 Test 4 Test 5
+12V1 4 A (48 W) 7 A (84 W) 11 A (132 W) 14.5 A (174 W) 17 A (204 W)
+12V2 3 A (36 W) 7 A (84 W) 10 A (120 W) 14 A (168 W) 17 A (204 W)
+5V 1 A (5 W) 2 A (10 W) 4 A (20 W) 5 A (25 W) 9 A (45 W)
+3.3 V 1 A (3.3 W) 2 A (6.6 W) 4 A (13.2 W) 5 A (16.5 W) 9 A (29.7 W)
+5VSB 1 A (5 W) 1 A (5 W) 1.5 A (7.5 W) 2 A (10 W) 2.5 A (12.5 W)
-12 V 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W) 0.5 A (6 W)
Total 104.2 W 196.6 W 299.3 W 398.3 W 499.2 W
% Max Load 20.8% 39.3% 59.9% 79.7% 99.8%
Room Temp. 45.7° C 45.6° C 45.5° C 45.7° C 48.3° C
PSU Temp. 48.5° C 48.5° C 49.1° C 49.7° C 49.1° C
Voltage Stability Pass Pass Pass Pass Pass
Ripple and Noise Pass Pass Pass Pass Pass
AC Power 127.3 W 235.6 W 362.2 W 489.3 W 629.0 W
Efficiency 81.9% 83.4% 82.6% 81.4% 79.4%
AC Voltage 109.8 V 109.1 V 107.8 V 107.1 V 106.7 V
Power Factor 0.978 0.99 0.995 0.997 0.998
Final Result Pass Pass Pass Pass Pass

With OCZ StealthXStream 500 W we faced an unusual limitation during test number five. With 500 W power supplies we usually pull 18 A from each +12 V input from our load tester and 6 A from +5 V and +3.3 V. However, under this configuration the power supply wouldn’t turn on, showing that over current protection (OCP) was configured at a very tight value. So the configuration for test five is different from the one we traditionally use and we had to pull a little bit more current/power from +5 V and +3.3 V then we’d like to. We also tried to overload this power supply, but we couldn’t: the unit would either not turn on or shut down after a few seconds. Since the goal of our overloading tests is to see the power supply protections working, we must say that they are in place and this unit didn’t burn or explode during our tests.

This unit could really deliver its labeled power at 48° C, which is terrific. Efficiency dropped a tiny little bit below the 80% mark when we pulled 500 W from it. Under other load patterns we saw efficiency varying between 81% and 83%, a satisfactory result that matches this product target audience (entry-level and mainstream users).

Voltage regulation was a highlight from StealthXStream 500 W, with all outputs (except -12 V) always within 3% from their nominal values, i.e., they were closer to their nominal values than required by ATX specification, which allows a tolerance of up to 5% for them.

Ripple and noise levels were always very low. Below you can see the results for test number five. The maximums allowed are 120 mV for +12 V and 50 mV for +5 V and +3.3 V. All values are peak-to-peak.

OCZ StealthXStream 500 W Power SupplyFigure 16: +12V1 input from our load tester with the power supply delivering 499.2 W (44.6 mV).

OCZ StealthXStream 500 W Power SupplyFigure 17: +12V2 input from our load tester with the power supply delivering 499.2 W (46.0 mV).

OCZ StealthXStream 500 W Power SupplyFigure 18: +5 V rail with the power supply delivering 499.2 W (12.0 mV).

OCZ StealthXStream 500 W Power SupplyFigure 19: +3.3 V rail with the power supply delivering 499.2 W (21.8 mV).

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Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.