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Corsair CS850M 850W Power Supply Review

Transient Response Tests

Advanced Transient Response Tests

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 to the PSU for 200ms while the PSU is working 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 tests are crucial since they simulate the transient loads a PSU is likely to handle (such as booting a RAID array, an instant 100-percent load of CPU/GPUs, etc.). We call these "Transient Response Tests," and they are designed to be tough to master.

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

20 Percent

VoltageBeforeAfterChangePass/Fail
12V12.160V11.994V1.37%Pass
5V5.046V4.921V2.48%Pass
3.3V3.329V3.172V4.72%Pass
5VSB5.005V4.963V0.84%Pass

50 Percent

VoltageBeforeAfterChangePass/Fail
12V12.106V11.981V1.03%Pass
5V5.016V4.892V2.47%Pass
3.3V3.303V3.148V4.69%Pass
5VSB4.957V4.907V1.01%Pass

Below 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

We measure the PSU's response in simpler transient-load scenarios—during the power-on phase of the PSU—in the next set of tests.

For the first measurement, we turn the PSU off, dial in the maximum current the 5VSB can output and then switch on the PSU. In the second test, we dial the maximum load +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 power or switch the PSU off by flipping its on/off switch), we dial the maximum load the +12V rail can handle before switching the PSU on 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 it is 5.5V for 5V).

All slopes ramp up smoothly during the turn-on tests, and we don't see any voltage overshoots or spikes. The PSU performs well enough in these metrics.

  • codygriffy
    Looks very nice!
    Reply
  • Shneiky
    Another CS PSU with bad caps and short life. And at 120 USD or more than 120 EUR as it appears in my district, this PSU does not stand a chance against the competition. Still a lot of people will buy it just because it has a Corsair name on it. I feel kinda bad that Corsair ruins their legacy of quality with products like CS and VS.
    Reply
  • giantbucket
    15746324 said:
    Another CS PSU with bad caps and short life. And at 120 USD or more than 120 EUR as it appears in my district, this PSU does not stand a chance against the competition. Still a lot of people will buy it just because it has a Corsair name on it. I feel kinda bad that Corsair ruins their legacy of quality with products like CS and VS.

    and then there are people who are going to hate on it just because it has a Corsair name on it...
    Reply
  • ykki
    Nice review! Can Tom's start a psu rating system (on a scale of 1 to 10)?
    Reply
  • Amdlova
    this perform really bad
    Reply
  • endeavour37a
    ykki, here is a tier list of PSUs, perhaps this is what your talking about.......
    http://www.tomshardware.com/forum/id-1804779/power-supply-unit-tier-list.html
    Reply
  • Sakkura
    Breaks ATX spec, high-ish 12V ripple, bad capacitors... No thanks.
    Reply
  • Shneiky
    ykki,

    I do not hate Corsair products because they are Corsair. I have a Corsair K70 and I love it. What I hate is cheaply made equipment that wants a price premium because it is X brand.
    Reply
  • Aris_Mp
    @ykki The relative performance graph can play this role and with much more accuracy. However it measures pure performance and doesn't take into account other factors as output noise, warranty period etc. For these factors a final rating is needed, indeed.
    Reply
  • damric
    Good review, Aris.

    I see no reason to buy this PSU when there are other good units with lower price built with better components. Example: Many XFX (Seasonic) and Golden Green (Capstone/B2) cost less but are more reliable with all good caps. Unfortunately, most consumers will be suckered in by the Corsair sticker.

    On the bright side, these Great Wall units have far less problems than the CX series. Probably even more reliable than the RM.
    Reply