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.

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38 comments
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  • codygriffy
    Looks very nice!
  • 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.
  • giantbucket
    550730 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...
  • ykki
    Nice review! Can Tom's start a psu rating system (on a scale of 1 to 10)?
  • Amdlova
    this perform really bad
  • 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
  • Sakkura
    Breaks ATX spec, high-ish 12V ripple, bad capacitors... No thanks.
  • 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.
  • 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.
  • 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.
  • endeavour37a
    The CS Series is made by Great Wall, any of their PSU made by Sea Sonic or Channel Well are good ones, so it just depends on which one you get on how the quality is.

    http://www.tomshardware.com/reviews/power-supply-psu-brands,3762-5.html
  • Sakkura
    1109232 said:
    The CS Series is made by Great Wall, any of their PSU made by Sea Sonic or Channel Well are good ones, so it just depends on which one you get on how the quality is. http://www.tomshardware.com/reviews/power-supply-psu-brands,3762-5.html


    You can't just say any Corsair units made by CWT are good. Their lowest-end series is the VS series, which is made by CWT. It's not better than these units made by Great Wall.

    Their Seasonic units are fine, but Corsair relies much less on Seasonic than it used to.
  • synphul
    I don't think it's so much that people want to hate on corsair because of their name, rather the reputation they've earned themselves. It only takes a little to earn a bad rep but takes a lot of turning that around to overcome and fix the way people regard them. Continuing to build low tier products at high prices and embracing low budget materials isn't doing them any favors.

    Companies like seasonic aren't nearly as heavily advertised and at that they're more recognized now than they used to be. Instead of cranking out tons of low quality components, they've concentrated on quality and maintained a good reputation. That's not saying every corsair is junk or seasonic never has a bad unit once in awhile. Corsair would rather flood the market with a lot of cheap units so they can't be surprised when many start avoiding the headaches and potential problems, instead investing the same money in better quality units.

    The review here is a bit confusing. On one hand it's a lower tier unit with a short(er) warranty, meant for moderate gaming. On the other it's powerful enough for 'enthusiast' builds with mulitple gpu's. Multiple gpu's are for 'moderate' gaming? If someone has an extra $300-500 for an additional gpu, surely they can muster up an additional $50 or so for a quality psu.
  • Aris_Mp
    this is a mid-level PSU, not a mainstream one, and with its true 850 W capacity can easily support at least two high-end VGAs, so it will do just fine into a gaming unit.

    Now as for the other matter you are referring, unfortunately many users while choose to invest a great amount on the mainboard, VGAs and CPU they leave the PSU for last so they buy one with the leftovers. Normally it should be the other way around since the PSU plays a key role in the health of all the rest system components.
  • endeavour37a
    551379 said:
    1109232 said:
    The CS Series is made by Great Wall, any of their PSU made by Sea Sonic or Channel Well are good ones, so it just depends on which one you get on how the quality is. http://www.tomshardware.com/reviews/power-supply-psu-brands,3762-5.html
    You can't just say any Corsair units made by CWT are good. Their lowest-end series is the VS series, which is made by CWT. It's not better than these units made by Great Wall. Their Seasonic units are fine, but Corsair relies much less on Seasonic than it used to.


    OK........
  • Shankovich
    Looks like someone read my comments on the 1600W superflower review :P.

    Looks like the OEM dropped the ball a bit. Not sure who is the CS series OEM? I think that amazing article from 2013 needs an update: http://www.tomshardware.com/reviews/power-supply-oem-manufacturer,2913-5.html
  • endeavour37a
    340939 said:
    Looks like someone read my comments on the 1600W superflower review :P. Looks like the OEM dropped the ball a bit. Not sure who is the CS series OEM? I think that amazing article from 2013 needs an update: http://www.tomshardware.com/reviews/power-supply-oem-manufacturer,2913-5.html


    Who's Who In Power Supplies, 2014: Brands Vs. Manufacturers
    http://www.tomshardware.com/reviews/power-supply-psu-brands,3762.html
  • daglesj
    Why would anyone want a 'flagship' PSU if their PC only pulls 400W at max load?
  • MasterMace
    Corsair did not build this as a gaming unit, despite being at the wattage for gaming. Having lower quality capacitors will not earn them any favors for gamers willing to drop $120 on a power supply.

    Corsair -raised- the price on their HX series. The HX 850M used to be well priced around $100-$110. I am not a fan of a company name being used to justify high prices, nor am I a fan of making worse quality products to raise the prices on old products.

    OEMs own their reputations longer than companies like Corsair who pay them to make it and slap their name on it after.
  • Shankovich
    Quote:
    340939 said:
    Looks like someone read my comments on the 1600W superflower review :P. Looks like the OEM dropped the ball a bit. Not sure who is the CS series OEM? I think that amazing article from 2013 needs an update: http://www.tomshardware.com/reviews/power-supply-oem-manufacturer,2913-5.html
    Who's Who In Power Supplies, 2014: Brands Vs. Manufacturers http://www.tomshardware.com/reviews/power-supply-psu-brands,3762.html


    Thank you hahaha, that's what I get for skipping over the links at the bottom of the page
  • ykki
    1109232 said:
    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


    Who doesn't know about that lol. I am talking of a numeric based system rather than a tier based one.
  • Aris_Mp
    Take a look below. In every review there is an updated graph.

    http://www.techpowerup.com/reviews/Andyson/Titanium_N700/10.html
  • JackNaylorPE
    At least Corsair continues to provide labeling sufficient for us to determine what models to avoid. "CS - Cheap S _ _ _"
  • damric
    35894 said:
    At least Corsair continues to provide labeling sufficient for us to determine what models to avoid. "CS - Cheap S _ _ _"


    X stands for DO NOT BUY.

    RM stands for RMA soon.