Cooler Master Real Power Pro 850 W Power Supply Review
Load Tests
Contents
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology. All the tests described below were taken with a room temperature between 47° C and 50° C. During our tests the power supply temperature was between 49° C and 52° C.
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.
+12V2 is the second +12V input from our load tester and during our tests we connected the power supply EPS12V connector to it (on this power supply EPS12V is half connected to the power supply +12V1 rail and half to the +12V2 rail).
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.
| 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) | 31 A (372 W) |
| +12V2 | 6 A (72 W) | 12 A (144 W) | 17 A (204 W) | 25 A (300 W) | 31 A (372 W) |
| +5V | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) | 10 A (50 W) |
| +3.3 V | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 W) | 10 A (33 W) |
| +5VSB | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 3 A (15 W) | 3.5 A (17.5 W) |
| -12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.8 A (9.6 W) |
| Total | 175.1 W | 353 W | 518 W | 696.9 W | 863 W |
| % Max Load | 20.6% | 41.5% | 60.9% | 82.0% | 101.5% |
| Room Temp. | 48.7° C | 47° C | 46.9° C | 49° C | 50° C |
| PSU Temp. | 52° C | 51.4° C | 48.8° C | 52° C | 52° C |
| Result | Pass | Pass | Pass | Pass | Pass |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 201 W | 401 W | 596 W | 826 W | 1,066 W |
| Efficiency | 87.1% | 88.0% | 86.9% | 84.4% | 81.0% |
This power supply could really deliver its labeled 850 W at a room temperature of 50° C with efficiency above 80% all the time, above 85% on tests one, two and three. If you only pull 350 W from this power supply it will work with an impressive 88% efficiency. Cooler Master says this product has 81% efficiency at 170 W, 85% efficiency at 425 W and 82% efficiency at 850 W. During our tests this power supply surpassed what the manufacturer says but at 850 W, which we saw efficiency at 1% below what the manufacturer says. This doesn’t mean that the manufacturer is lying, because usually the manufacturer measures efficiency at 220 V, which provides a higher efficiency compared to 115 V.
Voltage regulation during all our tests (including the overload tests we will present in the next page) was outstanding, with all outputs within 3% of their nominal voltages – ATX specification defines that all outputs must be within 5% of their nominal voltages (except on -12 V where the limit is 10%). In other words, on this power supply voltages were closer to their nominal numbers than what stated on the ATX specification.
Ripple and noise is another highlight from this product, as they were far below the maximum set by ATX spec (120 mV for +12 V and 50 mV for +5 V and +3.3 V). During our test number five – i.e., with the power supply delivering 860 W – noise level at +12V1 input from our load tester was 49 mV, noise level at +12V2 input from our load tester was 44.8 mV, noise level at +5 V was 33.2 mV and noise level at +3.3 V was 28.6 mV. Impressive results.
Figure 17: Noise level at +12V1 input from our load tester with the power supply delivering 860 W.
Figure 18: Noise level at +12V2 input from our load tester with the supply delivering 860 W.
Figure 19: Noise level at +5 V with power supply delivering 860 W.
Figure 20: Noise level at +3.3 V with power supply delivering 860 W.
The only “problem” we faced during our tests was with its over temperature protection (OTP). On this power supply this circuit only reads the status of the temperature sensor when you turn the power supply on. While the power supply is running it seems that this circuit is deactivated.
If you run the power supply with a high load for just a few minutes and then turn it off, it won’t turn back on until its secondary heatsink cools down. During our tests we thought that we had burned the power supply, but we waited a few minutes and the power supply went back to life.
We installed our thermometer probe on the secondary heatsink to see how OTP was configured. If the secondary heatsink is over 60° C, the power supply won’t turn on. The problem, like we said, is that apparently OTP doesn’t read the sensor while the power supply is running, because during normal operation under full load the temperature on the secondary heatsink reached as high as 80° C and the unit didn’t shut down – or OTP circuit is configured to shut down the power supply when the heatsink reaches a temperature so high that we couldn’t reach during normal operation at full load.
So if you buy this power supply and you see that it is not turning on, wait until it cools down.
Now let’s see if we can pull even more power from this product.