Rosewill Tachyon 750 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.”
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 the behavior of the reviewed unit 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 powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (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. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.
The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test, the +12VA and +12VB inputs were connected to the power supply single +12 V rail. (The +12VB input was connected to the power supply EPS12V connector.)
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | 5.5 A (66 W) | 11.5 A (138 W) | 17 A (204 W) | 22.5 A (270 W) | 27.5 A (330 W) |
| +12VB | 5.5 A (66 W) | 11 A (132 W) | 16.5 A (198 W) | 22 A (264 W) | 27.25 A (327 W) |
| +5 V | 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) | 1.5 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 | 154.4 W | 304.7 W | 458.4 W | 608.4 W | 749.8 W |
| % Max Load | 20.6% | 40.6% | 61.1% | 81.1% | 100.0% |
| Room Temp. | 46.8° C | 46.5° C | 47.1° C | 49.4° C | 48.4° C |
| PSU Temp. | 47.8° C | 47.9° C | 48.2° C | 49.3° C | 47.9° C |
| Voltage Regulation | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 169.3 W | 331.0 W | 500.1 W | 675.0 W | 849.0 W |
| Efficiency | 91.2% | 92.1% | 91.7% | 90.1% | 88.3% |
| AC Voltage | 118.1 V | 116.7 V | 113.6 V | 112.4 V | 110.7 V |
| Power Factor | 0.985 | 0.986 | 0.991 | 0.993 | 0.994 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
The 80 Plus Platinum certification promises efficiency of at least 90% under light (i.e., 20%) load, 92% under typical (i.e., 50%) load, and 89% under full (i.e., 100%) load. The Rosewill Tachyon 750 W matched these numbers, except during the full load test, in which it presented 88.3% efficiency. However, we have to consider that we tested this power supply at almost 50° C, while the 80 Plus certification tests are conducted at 23° C, and efficiency drops as temperature increases. Another explanation for the lower efficiency is because of the AC voltage, which was below 115 V during this particular test. On the other hand, we have excellent efficiency numbers for the other tests, in particular at light load, where we saw 91% efficiency.
Let’s discuss voltage regulation on the next page.