Corsair CS850M 850W Power Supply Review

Many enthusiasts don't have the budget for a flagship power supply, but still crave high efficiency to save money on electricity. They want enough capacity for a couple of powerful graphics cards, plus modular cables for trouble-free installation. Corsair's CS850M seems to fit this description. On top of that, it offers decent performance.

Corsair has a lot of power supplies in its portfolio, covering almost every conceivable market segment. Its CS family sits between the CX(M) and RM series. According to the company, it's above the mainstream line-up, addressing power users who want something better than a 80 PLUS Bronze-rated unit.

There are five CS models with capacities ranging from 450 to 850W. All of them sport 80 PLUS Gold efficiency, feature semi-modular cabling with low-profile and black modular cables and utilize Japanese primary capacitors. Those primary caps help ensure high reliability, though the secondary side's caps are critical as well (we'll discuss them all in more detail). The CS models are covered by three-year warranties since they occupy a lower tier of Corsair's power supply hierarchy. The higher-end models include five- to seven-year coverage. With this PSU, you get what you pay for. If warranty coverage is a big priority for you, consider buying a beefier unit.

In this review, we're looking at the CS line's highest-output implementation. According to Corsair, the CS850M is ideal for moderate gaming, though we know it'll drive a machine with two powerful graphics cards installed. Clearly, the folks at Corsair believe that anyone interested in a CS model will want it for lower power consumption and a more conservative price tag. The reality is that if you leave your PC on all day, even at low loads, an 80 PLUS Gold-rated PSU could save you enough money over time to justify its purchase.

You probably won't see a noticeable difference switching from an 80 PLUS Gold PSU to a Platinum one, but the difference between an 80 PLUS Bronze and Gold-rated unit is significant. In addition, PSUs age. After years of continuous use, their performance degrades. If they employ high-quality capacitors, this process is slow. But if they use cheaper Chinese caps, the loss of performance is more severe as time passes. And once an old PSU stops working, it can take out other components in your system. So pay attention to sudden restarts and stability problems as your PSU gets older.

Specifications

The CS850M's efficiency is enough to meet the 80 PLUS Gold requirements, and it utilizes a semi-modular design with only two fixed cables. Like most PSUs in this price range, the CS850M is Haswell-ready, meaning that it can deliver full load on the minor rails with minimum load at +12V, with all of its rails within the ATX specification's ranges.

Corsair specs a maximum operating temperature of 40 degrees C. You won't be able to abuse this PSU because it doesn’t use high-quality capacitors like the company's higher-end models. All of the protections we look for are enabled except for over-current protection (which simply isn't needed in a high-capacity single-rail power supply). A sleeve bearing fan is tapped for cooling, since ball-bearing fans are more expensive and Corsair wants to keep the price of this unit as low as possible. Finally, the dimensions of the PSU are compact and the provided warranty of three years is satisfactory for a mid-category PSU, although a longer warranty would have been nice.

Power Specifications

Rail3.3V5V12V5VSB-12V
Max. PowerAmps252570.830.8
Watts130849.6153.6
Total Max. Power (W)850

There is only one +12V rail, which can deliver almost 71A. Again, it should drive a fairly high-end PC with a couple of potent graphics cards installed. The minor rails offer up to 130W combined power, which is ample for any modern PC. The 5VSB rail is powerful enough for the needs of an average user.

Cables And Connectors

Native Cables
ATX connector (620mm)20+4 pin
4+4 pin EPS12V (670mm)1
Modular Cables
6+2 pin PCIe (600mm+150mm)4
SATA (500mm+95mm+95mm+95mm)8
4 pin Molex (450mm+100mm+100mm)6
FDD(+100mm)2

Only two cables are fixed, which is fine since they're essential for every new PC build anyway. Cable length is adequate overall, though the distance between the four-pin Molex connectors could be problematic. Typically, the components powered by these connectors are far from each other (think case fans). But Corsair puts them fairly close together. On the plus side, short runs between the SATA connectors are ideal since hard drives and SSDs are typically right next to each other. Finally, all connectors use 18AWG wires, which are recommended by the ATX spec.

The number of PCIe, SATA and four-pin Molex connectors is good, given this unit's capacity. However, Corsair equips the CS850M with just one EPS connector. Normally, an 850W PSU should have two of them. In addition to server-oriented mainboards, some X99 platforms also require two EPS connectors (or one EPS and one ATX12V). If you plan to use this PSU with one of those motherboards, you'll need to use adapters, and we try to avoid those. Lots of current can pass through EPS and PCIe cables, and the use of adapters can lead to problems. Four-pin Molex connectors are used to attach adapters, and they were designed for such high amperage. On top of that, using adapters leads to increased wire resistance. In short, if your machine needs two EPS connectors or more PCIe connectivity, buy a PSU that covers those requirements. 

Power Distribution

Since this PSU features a single +12V rail, there isn’t much to say about its power distribution.

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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.