Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.
Advanced Transient Response Tests
For details about our transient response testing, please click here.
In the real world, power supplies are always working with loads that change. It's of immense importance, then, for the PSU to keep its rails within the ATX specification's defined ranges. The smaller the deviations, the more stable your PC will be with less stress applied to its components.
We should note that the ATX spec requires capacitive loading during the transient rests, but in our methodology, we also choose to apply a worst case scenario with no additional capacitance on the rails.
Advanced Transient Response at 20% – 200ms
Advanced Transient Response at 20% – 20ms
Advanced Transient Response at 20% – 1ms
Advanced Transient Response at 50% – 200ms
Advanced Transient Response at 50% – 20ms
Advanced Transient Response at 50% – 1ms
Results 25-29: Transient Response
The transient response at +12V is good, but the previous generation Focus performs even better here. On the minor rails, 5V and 3.3V, the transient performance is not so impressive. Especially at 3.3V in four tests, the voltage dropped lower than 3.14V, going out of the ATX spec's requirements.
Turn-On Transient Tests
In the next set of tests, we measure the PSU's response in simpler transient load scenarios—during its power-on phase. Ideally, we don't want to see any voltage overshoots or spikes since those put a lot of stress on the DC-DC converters of installed components.
Turn-On Transient Response Scope Shots
The performance is good in the turn-on transient tests. There are no high spikes and voltage overshoots. It just takes a little longer for the +12V rail to increase its level to the nominal voltage.
Power Supply Timing Tests
There are several signals generated by the power supply, which need to be within specified, by the ATX spec, ranges. If they are not, there can be compatibility issues with other system parts, especially mainboards. From year 2020, the PSU's Power-on time (T1) has to be lower than 150ms and the PWR_OK delay (T3) from 100 to 150ms.
|T1 (Power-on time) & T3 (PWR_OK delay)|
The Power-on time is within 100ms, but the power-ok delay is much higher than 150ms, so the PSU does not support the alternative sleep mode, which will be a requirement by the ATX v2.52 from 2020.
Ripple represent the AC fluctuations (periodic) and noise (random) found in the PSU's DC rails. This phenomenon significantly decreases the capacitors' lifespan because it causes them to run hotter. A 10-degree Celsius increase can cut into a cap's useful life by 50%. Ripple also plays an important role in overall system stability, especially when overclocking is involved.
The ripple limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V, and 5VSB).
|10% Load||9.4 mV||7.3 mV||11.5 mV||8.8 mV||Pass|
|20% Load||13.9 mV||8.0 mV||12.4 mV||9.4 mV||Pass|
|30% Load||16.6 mV||8.8 mV||12.8 mV||8.8 mV||Pass|
|40% Load||19.4 mV||9.5 mV||14.0 mV||9.0 mV||Pass|
|50% Load||20.5 mV||10.0 mV||14.7 mV||9.1 mV||Pass|
|60% Load||21.6 mV||10.3 mV||15.2 mV||9.2 mV||Pass|
|70% Load||21.4 mV||10.7 mV||15.2 mV||9.5 mV||Pass|
|80% Load||22.2 mV||11.6 mV||18.1 mV||10.0 mV||Pass|
|90% Load||23.3 mV||12.2 mV||18.6 mV||10.4 mV||Pass|
|100% Load||34.9 mV||14.6 mV||19.1 mV||12.6 mV||Pass|
|110% Load||37.6 mV||15.0 mV||20.0 mV||12.9 mV||Pass|
|Crossload 1||15.7 mV||11.3 mV||18.7 mV||9.6 mV||Pass|
|Crossload 2||35.0 mV||10.7 mV||14.0 mV||12.2 mV||Pass|
Results 30-33: Ripple Suppression
The ripple suppression is satisfactory, but there is a significant difference between the 90% and 100% load ripple results at +12V.
Ripple At Full Load
Ripple Full Load Scope Shots
Ripple At 110% Load
Ripple 110% Load Scope Shots
Ripple At Cross-Load 1
Ripple CL1 Load Scope Shots
Ripple At Cross-Load 2
Ripple CL2 Load Scope Shots
EMC Pre-Compliance Testing – Average & Peak EMI Detector Results
Electromagnetic Compatibility (EMC) is the ability of a device to operate properly in its environment without disrupting the proper operation of other close-by devices.
Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other close-by devices if too high. For example, it can be the cause of increased static noise in your headphones or/and speakers.
With the AVG EMI detector, we see two spurs exceeding the corresponding limits, but with the Quasi-Peak detector, everything seems fine. Nonetheless, we would like to see lower EMI emissions with the QP detector below 1MHz.
MORE: Best Power Supplies
MORE: All Power Supply Content
Current page: Transient Response Tests, Timing Tests, Ripple Measurements and EMC Pre-Compliance TestingPrev Page Protection Features, DC Power Sequencing, Cross-Load Tests and Infrared Images Next Page Performance, Noise and Efficiency
Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.