BFG MX-550 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 sligh
tly 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 +12V1 rail (EPS12V connector).
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 4 A (48 W) | 8 A (96 W) | 12 A (144 W) | 16 A (192 W) | 20 A (240 W) |
| +12V2 | 4 A (48 W) | 8 A (96 W) | 12 A (144 W) | 16 A (192 W) | 20 A (240 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 5 A (25 W) | 6 A (30 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 5 A (16.5 W) | 6 A (19.8 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 | 115.9 W | 223.3 W | 338.0 W | 442.0 W | 544.9 W |
| % Max Load | 21.1% | 40.6% | 61.5% | 80.4% | 99.1% |
| Room Temp. | 46.9° C | 46.9° C | 47.3° C | 47.3° C | 50.1° C |
| PSU Temp. | 49.1° C | 49.1° C | 50.3° C | 50.3° C | 53.1° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 134 W | 254 W | 391 W | 523 W | 668 W |
| Efficiency | 86.5% | 87.9% | 86.4% | 84.5% | 81.6% |
| Final Result | Pass | Pass | Pass | Pass | Pass |
BFG MX-550 showed to be an excellent product. It could deliver its labeled power at 50° C.
If you pull up to 80% (440 W) from it, it will deliver at least 84.5% efficiency. Working with it at up to 60% (330 W) from its labeled maximum capacity you will see efficiency between 86% and 88%, which is terrific. Pulling its full labeled power efficiency dropped to 81.6% – not as great as the other results but still above the 80% mark.
Voltage stability was impressive, with all outputs always within 3% from their nominal values (the maximum allowed is 5% – 10% for -12 V), including -12 V.
Noise level was always far below the maximum allowed. During test number five (550 W) this unit presented a noise level of 22.6 mV at +12V1, 24 mV at +12V2, 16.6 mV at +5 V and 13.4 mV at +3.3 V. 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.
Now let’s see if we could pull even more power from MX-550.