be quiet! Pure Power 9 600W PSU Review

Transient Response Tests

Advanced Transient Response Tests

For details on our transient response testing, please click here.

In these tests, we monitor the response of the PSU in two different scenarios. First, a transient load (10A at +12V, 5A at 5V, 5A at 3.3V and 0.5A at 5VSB) is applied for 200ms while the PSU works at 20 percent load. In the second scenario, the PSU is hit by the same transient load while operating at 50 percent load. In both tests, we use our oscilloscope to measure the voltage drops caused by the transient load. The voltages should remain within the ATX specification's regulation limits.

These metrics are crucial because they simulate the transient loads a PSU is likely to handle (such as booting a RAID array or an instant 100 percent load of CPU/GPUs). We call them "Advanced Transient Response Tests," and they are designed to be very tough to master, especially for PSUs with less than 500W capacity.

Advanced Transient Response at 20 Percent

VoltageBeforeAfterChangePass/Fail
12V12.125V11.950V1.44%Pass
5V5.005V4.922V1.66%Pass
3.3V3.336V3.179V4.71%Pass
5VSB5.003V4.971V0.64%Pass

Advanced Transient Response at 50 Percent

VoltageBeforeAfterChangePass/Fail
12V11.995V11.810V1.54%Pass
5V4.991V4.903V1.76%Pass
3.3V3.300V3.132V5.09%Fail
5VSB4.960V4.921V0.79%Pass

The +12V rail's performance in these tests isn't the best, that's for sure. However, voltage drops are controlled well in light of the fact that an ACRF topology cannot handle transient loads as deftly as other designs. When you look at the oscilloscope shots below, though, you'll see it takes quite some time for the +12V rail to stabilize whenever a transient load is applied. The same goes for the 5V and 5VSB rails, which have low voltage drops. Finally, deviations on the 3.3V rail are large, leading to a fail during the second test.

Here are the oscilloscope screenshots we took during Advanced Transient Response Testing:

Transient Response At 20 Percent Load

Transient Response At 50 Percent Load

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.

For the first measurement, we turn off the PSU, dial in the maximum current the 5VSB can output and switch on the PSU. In the second test, we dial the maximum load the +12V can handle and start the PSU while it's in standby mode. In the last test, while the PSU is completely switched off (we cut off the power or switch off the PSU by flipping its on/off switch), we dial the maximum load the +12V rail can handle before switching on the PSU from the loader and restoring power. The ATX specification states that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12V is 13.2V, and 5.5V for 5V).

There is a notable spike at 5VSB, though it's below the limit. We notice two voltage overshoots at +12V, but they are way lower than the corresponding limit (13.2V). 

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  • turkey3_scratch
    Really poor unit. For one thing, the crossload performance is poor. Sleeve bearing fan with less reliability. 85C primary capacitor. Once again, another failed 3.3V transient response. Very high inrush current. Also, near worst of all, 140+mv of ripple on the 12V rail in CL2. Just really bad. And CL2 is a realistic scenario these days because those 3.3V and 5V rails don't do much anyway. FSP's soldering is clearly not the same as the nice soldering on their high end units.

    But my largest complaint would have to be voltage regulation (line regulation) under different load scenarios on page 6.
  • 4745454b
    85C main cap doesn't bother me that much. It should get airflow from the fan so unless the fan dies (and if it does 105C cap isn't going to help much.) or it gets clogged with dust you should be ok. As for the CL test what do you expect? It's a group regulated design so that's going to happen. It's like buying a super duty truck and then complaining you don't get 30MPG in town. What I find more bothersome is they can't seem to sell you what they claim on the box. If it's not C6 or C7 ready and not a group reg design, why claim so? I wonder if they shipped the wrong unit?
  • powernod
    Outstanding review by Aris as always! :)
    If only the PSU itself was outstanding as well:ouch:
  • basroil
    Looks like FSP is still mostly a second tier manufacture with those transient response and inrush... does it really hurt that much to put a shuntable thermistor like Seasonic and SuperFlower units have?

    For less than $10 more you can usually find excellent Seasonic and SuperFlower Leadex Gold units, which makes it really hard to say this PSU is anything more than "meh"
  • Aris_Mp
    actually I am worried about the bulk cap, because 85C means that it has 4x times lower lifetime than a 105C cap.
  • turkey3_scratch
    Anonymous said:
    85C main cap doesn't bother me that much. It should get airflow from the fan so unless the fan dies (and if it does 105C cap isn't going to help much.) or it gets clogged with dust you should be ok. As for the CL test what do you expect? It's a group regulated design so that's going to happen. It's like buying a super duty truck and then complaining you don't get 30MPG in town. What I find more bothersome is they can't seem to sell you what they claim on the box. If it's not C6 or C7 ready and not a group reg design, why claim so? I wonder if they shipped the wrong unit?


    Not all group regulated designs are exactly the same way. We see in Seasonic's S12ii series a group regulated design that actually crossloads very well. This seems to be one of the worst on the ladder.

    @Aris: Why is Inactive PWR_OK to DC_LOSS better at a higher value? Once the PWR_OK signal is dropped, wouldn't you want the unit to shut down as quickly as possible, not prolong it?
  • powernod
    It was already explained by Aris at his review:
    "The power-good signal lasts longer, so when it drops, the voltage level of the +12V rail is already below 11V."
    When the pwr_ok to DC_loss is higher (*meaning that it has a positive , not negative value) that means that the motherboard will already have been shut-down. (*from what i've understand, at least)
  • turkey3_scratch
    Not sure how the motherboard could shut down before the PWR_OK signal is dropped.
  • Aris_Mp
    the problem is that in some PSUs, PWR_OK, which informs the mainboard when it should shut down, drops after and not before the rails go our of spec. So once it drops the rails are already too low.

    Normally when AC is removed, the PWR_OK signal should be de-asserted at least 1ms before voltages go out of spec in order not to stress the VRMs of the mainboard and of other components (e.g. VGA, HDD, SSD, etc.).

    The only way to address this issue is to have a circuit on the mainboard checking the input voltages and give the shut down order when these go out of spec. In other words to completely bypass the power_ok signal coming from the PSU. But this will cost money and after all a PSU oughts to follow ATX spec's guidelines.
  • turkey3_scratch
    So is "DC_LOSS" considered "voltages out of spec"? I mean, there can still be DC even if voltages are out of spec. It won't be a loss of DC< just an out-of-spec voltage relative to the DC.
  • Aris_Mp
    Anonymous said:
    So is "DC_LOSS" considered "voltages out of spec"? I mean, there can still be DC even if voltages are out of spec. It won't be a loss of DC< just an out-of-spec voltage relative to the DC.


    Yes there can still be DC when voltages are out of spec, since for example 12V don't drop to 0V instantly.

  • kunstderfugue
    Oh god an FSP. Let's see how it does.
  • kunstderfugue
    $74.90 suggested price, this thing is going to get destroyed in price to performance. You can get a G2 which has a fanless mode for $5 more.
  • RedJaron
    Anonymous said:
    Oh god an FSP. Let's see how it does.

    Why say that? While this model may not be lacking, plenty of FSP's other models are great.