BFG MX-680 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.
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 out tests the +12V1 input was connected to the power supply +12V1 (main motherboard cable and peripheral power connectors) and +12V3 rails (video card auxiliary power connector), while the +12V2 input was connected to the power supply +12V2 rail (EPS12V connector).
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 5 A (60 W) | 10.5 A (126 W) | 15.5 A (186 W) | 20.5 A (246 W) | 25.5 A (306 W) |
| +12V2 | 5 A (60 W) | 10.5 A (126 W) | 15.5 A (186 W) | 20.5 A (246 W) | 25.5 A (306 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 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 | 138.4 W | 276.7 W | 412.7 W | 546.6 W | 678.4 W |
| % Max Load | 20.4% | 40.7% | 60.7% | 80.4% | 99.8% |
| Room Temp. | 47.6° C | 46.6° C | 49.1° C | 49.8° C | 48.6° C |
| PSU Temp. | 47.4° C | 48.0° C | 49.8° C | 55.3° C | 53.5° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Failed on -12 V | Failed on -12 V | Pass | Pass |
| AC Power | 168.5 W | 330.8 W | 500.7 W | 680.0 W | 877.0 W |
| Efficiency | 82.1% | 83.6% | 82.4% | 80.4% | 77.4% |
| AC Voltage | 113.1 V | 113.2 V | 111.7 V | 108.8 V | 105.4 V |
| Power Factor | 0.986 | 0.996 | 0.998 | 0.998 | 0.999 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
BFG MX-680 could really deliver 680 W at 48.6° C. If you pull up to 60% from its labeled capacity (i.e., up to 408 W) you will see a decent efficiency between 82.1% and 83.6%. When pulling 80% from its labeled power (i.e., 544 W) efficiency dropped to 80.4%, still above the 80% mark. But at full load (680 W) efficiency dropped below 80%, at 77.4%.
It is always good to remember that this is not necessarily a bad thing, as you probably won’t pull anywhere near its labeled capacity, as power supplies are designed for you to run them at 50% from their labeled capacity (click here to understand more).
The only problem we had with this power supply was with its -12 V output. During tests number one and five the ripple level from this output was low (18.4 mV and 38.4 mV, respectively) and during test number four it was high (93 mV), but still inside the 120 mV limit. But during tests number two and three the ripple on this output skyrocketed to 365 mV and 480 mV, respectively, far higher than the maximum allowed (120 mV).
Figure 16: Noise level on -12 V during test number four (480 mV).
All other outputs presented very low noise levels, as you can see on the screenshots below. Just to remember, the maximum allowed for the +12 V outputs is 120 mV and the maximum allowed for the +5 V and +3.3 V outputs is 50 mV. All these values are peak-to-peak figures.
Figure 17: +12V1 input from load tester at 678.4 W (35.6 mV).
Figure 18: +12V2 input from load tester at 678.4 W (35.2 mV).
Figure 19: +5V rail with power supply delivering 678.4 W (18.2 mV).
Figure 20: +3.3 V rail with power supply delivering 678.4 W (15.6 mV).
Now let’s see if we could pull even more power from MX-680.
