We made 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 loads patterns, trying to pull around 20%, 40%, 60%, 80% and 100% of its labeled maximum capacity (under “% Max Load” we list the actual percentage that was used), watching how the reviewed unit behaved under each load. On the table below we list the load patterns we used and the results for each load.
For the 100% load test we faced a challenge. The +12V2 input from our load tester was exclusively connected to the power supply +12V2 rail thru its EPS12V connector (+12V1 input was connected at the same time to the power supply +12V1 and +12V3 rails), and the power supply over current protection circuit (OCP) wouldn’t allow us to pull more than 25 A from this rail. We wanted to pull 850 W by configuring 10 A at +5 V and +3.3 V and 31 A from each +12V input from our tester, but due to this limitation we had to configure our load tester differently. The configuration used wasn’t that bad, as we could still pull 33 A from the +12V1 input (+12V1 and +12V3 rails) and 25 A from +12V2, while maintaining +5 V and +3.3 V at 16 A.
As you may already know by reading our reviews, we always try to pull the maximum we can from the +12 V outputs, as video cards and CPUs are connected to +12 V and thus this output is the one that is most loaded, especially on a high-end PC.
If you add all the powers listed for each test you may find a value different from what posted under “Total” below. Since each output can have a slight variation (e.g. +5 V output working at 5.10 V) the actual total amount of power being delivered is slightly different from the calculated value. On “Total” row we are using the real amount of power being delivered, as measured by our load tester.
Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
+12V1 | 6 A (72 W) | 13 A (156 W) | 20 A (240 W) | 25 A (300 W) | 33 A (396 W) |
+12V2 | 6 A (72 W) | 12 A (144 W) | 17 A (204 W) | 25 A (300 W) | 25 A (300 W) |
+5V | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) | 16 A (80 W) |
+3.3 V | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 W) | 16 A (52.8 W) |
+5VSB | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5 W) | 3 A (15 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 | 172.3 W | 347.1 W | 508.9 W | 681.9 W | 844.8 W |
% Max Load | 20.3% | 40.9% | 59.9% | 80.2% | 99.4% |
Room Temp. | 48.8º C | 48.1º C | 47.6º C | 45.9º C | 48.9º C |
PSU Temp. | 47.6º C | 48.2º C | 47.7º C | 45.8º C | 48.7º C |
Voltage Stability | Pass | Pass | Pass | Pass | Pass |
Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
AC Power (1) | 194 W | 387 W | 578 W | 795 W | 1,031 W |
Efficiency (1) | 88.8% | 89.7% | 88.0% | 85.8% | 81.9% |
| AC Power (2) | 202.8 W | 404.4 W | 601.2 W | 825.0 W | 1,063 W |
| Efficiency (2) | 85.0% | 85.8% | 84.6% | 82.7% | 79.5% |
| AC Voltage | 112.5 V | 110.4 V | 108.4 V | 106.3 V | 103.1 V |
| Power Factor | 0.992 | 0.995 | 0.997 | 0.997 | 0.997 |
Final Result | Pass | Pass | Pass | Pass | Pass |
Updated 07/03/2009: 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.
Efficiency was very high when we pulled up to 60% of the labeled load (i.e. up to 510 W), being between 84.6% and 85.8%. At 80% load (680 W) efficiency was still decent at 82.7%. However pulling 850 W from it efficiency dropped to 79.5%.
Voltage stability was another highlight from CP-850, with all voltages inside 3% of their nominal values, i.e. voltages were closer to their nominal value than needed, as ATX spec allows voltages to be up to 5% from their nominal values (10% for -12 V).
And finally we have noise and ripple, which were very low all the time. Below you can see the results for test number five. As we always point out the limits are 120 mV for +12 V and 50 mV for +5 V and +3.3 V and all numbers are peak-to-peak figures.
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Figure 18: +12V1 input from load tester with power supply delivering 844.8 W (17.8 mV).
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Figure 19: +12V2 input from load tester with power supply delivering 844.8 W (12.6 mV).
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Figure 20: +5V rail with power supply delivering 844.8 W (13.2 mV).
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Figure 21: +3.3 V rail with power supply delivering 844.8 W (15.2 mV).
Let’s now see if we could pull more than 850 W from this unit.
