Corsair RM550x Power Supply Review

Pros, Cons And Final Verdict

CWT, under Corsair's guidance, manufactures several excellent PSU families, including the RMi and RMx. The only differences between them is the lack of a digital interface and a rifle bearing fan in the RMx models, which push their prices down. Indeed, many enthusiasts don't care about the RMi's digital goodies, preferring simpler (and less expensive) alternatives. I personally believe that the ability to monitor a PSU's operation and control its fan is important. But I also understand that not everyone shares my opinion.

Regardless, the RMi line-up doesn't even include a 550W member, so the RM550x stands alone in Corsair's portfolio. The competition is pretty compelling; EVGA's 550 G2 is probably the most noteworthy opponent. Compared to that power supply, the RM550x features even better performance and quieter operation. In fact, Corsair's offering more closely resembles a passive PSU than a normal one. Its semi-passive operation lasts for a long time, and even when the fan engages, it spins slowly. We had to push the PSU very hard to get its fan to register more than 30 dB(A). Normally we would be a little skeptical about the reliability of a PSU without heat sinks on its secondary side and such an unobtrusive fan. However, Corsair appears to be very confident in CWT's design. Otherwise it wouldn't equip the RM550x with a seven-year warranty. 

The RM550x is an amazing PSU with fantastic ripple suppression, tight load regulation on the minor rails and excellent performance with transient loads. The cherry on top is nearly silent operation. On top of that, this unit is highly efficient, although some other Gold-rated PSUs with similar capacity fare a bit better. Another advantage of the RM550x is the quality of its internal components. The only thing that we would like to see in this PSU is a convenient way to test the fan's proper operation. The fan does spin for a short time every time the power supply is switched on, but we'd like Corsair to add a fan test button like the one on its RMi units.

In general, it is really hard to find any flaws in a PSU like this. We're extra-picky though, so we would like to see even tighter load regulation on the +12V rail. Finally, it would be nice if Corsair dropped its price closer to 90 bucks. That'd increase the RM550x's performance per dollar ratio, bringing its value more in line with EVGA's 550 G2, which previously dominated the mid-wattage category alongside the 650 G2.

MORE: Best Power Supplies
MORE: Power Supplies 101
MORE: How We Test Power Supplies
MORE: All Power Supply Content

Aris Mpitziopoulos is a Contributing Editor for Tom's Hardware, covering Power Supplies.

Follow us on Twitter @tomshardware, on Facebook and on Google+.

This thread is closed for comments
36 comments
    Your comment
  • Dark Lord of Tech
    I just wish they would get the price down , these are a great lineup \ RX.
  • basroil
    From the performance it seems like CWT is finally something to consider... It's showing Leadex Gold/Seasonic levels of performance.
  • Dark Lord of Tech
    I love the RMX and RMI series , price just keeps me away from the purchase , very very solid.

    Knock a little off the price and these would fly out of warehouses.
  • William Henrickson
    They were on sale when new. I snagged an RM750i for $105 -w- shipping
  • Dark Lord of Tech
    Yeah the 550w should be about 79.99 to 89.99 , no rebates.

    Then I would grab a few.
  • JQB45
    Quote:
    Yeah the 550w should be about 79.99 to 89.99 , no rebates. Then I would grab a few.


    Corsair RMx 550W 80+ Gold Certified Fully-Modular ATX Power Supply
    http://pcpartpicker.com/part/corsair-power-supply-cp9020090na
    $79.99

    $89.99 for the 650W version.

    UPDATE:

    Sorry thats with mail in rebates...
  • Dark Lord of Tech
    I don't do rebates , takes to long , and maybe you get it maybe you don't , I'll wait for a newegg drop.
  • Nintendork
    We really need more platinum/titanium PSU's at 300-500w. Most PC's stays near idle and with the efficiency focused gpu's/cpu's they rarely exceed 100w unless you tax them.
  • turkey3_scratch
    Plus companies often don't even send you the rebates, sometimes they just say it was too late or some other bull crap like that. I agree with Blackbird. I've been waiting for a review of the 550 RMx, and what I get out of this review is that it trades blows with the 550 G2 that saying one or the other is better is just silly and extremely nit-picky. They are both incredible. Both offer a 7 year warranty, as only higher-wattage G2s offer the 10 year warranty. They are just so close, that when it comes to picking the better one, the cheaper one is better, and the G2 is cheaper.

    I've actually quit including rebates in my pcpartpicker lists. They are a pain and I don't think they reflect the true cost of an item.
  • turkey3_scratch
    205977 said:
    We really need more platinum/titanium PSU's at 300-500w. Most PC's stays near idle and with the efficiency focused gpu's/cpu's they rarely exceed 100w unless you tax them.


    I wish so, but unfortunately if this were to happen they would end up priced the same as any Platinnum/Titanium 650W unit. It's just the way it works. Quality low-wattage models are priced almost the same as the higher-wattage models. I would like to see something like a Titanium 250W model come out from Seasonic. Something like $40, fully modular. Will never happen, though.
  • logainofhades
    Yea the price for these is a big turn off. It is selling at a price that the Evga G2 750w is often seen at. The Evga P2 650w even sells for less. There are quite a few Seasonic and Superflower based units, cheaper than this, actually.
  • turkey3_scratch
    The Seasonic Platinum Series is quite expensive, and much of the X-Series is not even sold anymore. Only the S12ii comes to my mind as an option under $60.
  • logainofhades
    The cheapest RM550x is $99, before rebate, at newegg. You can get a G2 and P2 Evga for same or less. Seasonic 550g is selling for $69. Even if I needed a fully modular unit, there are less expensive models from Evga, XFX, and Antec. For a few $$ more, I can get a GS 850w or a G2 750w. The pricing on this unit is just not good enough to compete. Even their own 650w RMX is only about $10 more.

    http://pcpartpicker.com/parts/power-supply/#e=5,4&W=550,2000&sort=a9&page=1&m=52,11,14,71,39&p=1,2
  • turkey3_scratch
    Well I know that's what I said, I can't find a good argument as to why one should purchase the RMx for $20 more than the EVGA G2, so I just don't recommend it.
  • powernod
    I've got one very good reason for you: The fantastic performance of Corsair's /CWT's platform at the new "Power-OK signal" tests that Aris added at his reviews. On the contrary, the performance of Leadex's platform (*in which EVGA's G2 units are based) in these tests is very discouraging ( http://www.tomshardware.com/reviews/super-flower-leadex-gold-550w-power-supply,4416-4.html )
  • logainofhades
    Still cannot see spending $99 on a 550w Corsair, when I can get a 650w P2, for the same price. Heck, the Seasonic built GS 850w is selling for a mere $3 more.
  • turkey3_scratch
    Yes G2 hold-up time is 12ms whereas ATX spec is 16ms, but that doesn't mean the PSU is going to cause damage to the computer, it just means that if there is AC loss for 12ms the computer will shut down, as the PSU won't be able to maintain the DC. Better hold-up time is not worth the additional $20, especially if you're not running something like a server, in which you would have a UPS anyway that quickly kicks on the battery power in 12ms or less (you'd do research to buy one that does so, as some may be higher than 12ms).

    I'd say the hold-up time is a small gripe and not enough for a $20 more PSU. If hold-up time as super important, every PSU reviewer site would test it like Jonnyguru.
  • powernod
    Quote:
    Better hold-up time is not worth the additional $20, especially if you're not running something like a server, in which you would have a UPS anyway that quickly kicks on the battery power in 12ms or less (you'd do research to buy one that does so, as some may be higher than 12ms).


    Indeed, those who have a good UPS to protect their system, they shouldn't worry about that, but if you don't have a UPS, this failure at Hold-UP time /Power-OK signal, could be very dangerous.
  • turkey3_scratch
    2077519 said:
    Quote:
    Better hold-up time is not worth the additional $20, especially if you're not running something like a server, in which you would have a UPS anyway that quickly kicks on the battery power in 12ms or less (you'd do research to buy one that does so, as some may be higher than 12ms).
    Indeed, those who have a good UPS to protect their system, they shouldn't worry about that, but if you don't have a UPS, this failure at Hold-UP time /Power-OK signal, could be very dangerous.


    How would hold-up time be dangerous?
  • powernod
    I didn't say only Hold-up Time, I was referring at Aris's new test for Power-OK signal. Take a look of one of his analysis : " The hold-up time tests don't go well. Not only is the measured hold-up less than 16ms (the ATX spec's minimum), but the Power_OK signal drops after, and not before, the PSU's rails go out of spec. This means that your motherboard gets a false power-good signal from the PSU. Indeed, we measured the +12V rail floating at around 10.8V when Power_OK dropped to zero. This is a very low voltage level that applies lots of stress to the voltage regulators of components fed by +12V " ( http://www.tomshardware.com/reviews/super-flower-leadex-gold-550w-power-supply,4416-4.html )
  • turkey3_scratch
    That is the Superflower Leadex 550W where the Pwr_OK signal drops after the voltage is below 10.8V, and while the EVGA 550 G2 is based off that unit, Aris does not mention that same behavior for the G2 on the 550 G2 review. So it is possible the 550 G2 does not have this same mistake, but I am unsure myself. They could have made modifications.

    Edit: Ahh, he didn't check AC loss to PWR_OK in the G2 review, so the behavior is most likely still present.
  • turkey3_scratch
    This behavior is also present on Sirfa-made units, which have very high AC loss to PWR_OK off hold up times because their PWR_OK signal does not turn off until the voltage is somewhere below like 10.2V! http://www.jonnyguru.com/forums/showthread.php?t=12886

    The real question though is how fatal, in terms of the 550 G2, this really is. Is the 10.8V+ applied to the unit's VRM components for 12ms really going to harm the unit fatally? If anything, those Sirfa units are more dangerous. A higher AC loss to PWR_OK loss time is not necessarily good if the voltage is too low. They should be setting the threshold to 11.4V, not these lower values, so shame on Superflower and Sirfa for this. But it's actually a good thing the 550 G2 is only 12ms, you don't want those low voltages to be handled by the 12V VRM components for any longer, shorter is better in this case. But yes you are correct, they should improve these, but again does this merit the $20 extra for the 550 RMx? I'd have to ask a PSU expert how much of a harm this 10.8V+ for 12ms will make, as I'm not an expert on that.
  • Aris_Mp
    hold-up time tests are not the easiest thing to do since besides extra equipment you also need GOOD knowledge of what you are doing. On top of that in order to measure hold-up time along with power good time and other stuff as well you need an accurate (thus expensive) four channel, at least, scope. Till I raised enough money to buy one I didn't have the capability to measure both hold-up times so I provided only the power good signal's time.

    If your PSU has a really short hold-up time in some cases your UPS won't be able to handle the job, especially if its transfer time is higher than 15-20ms. Moreover the longer the PSU goes without power, the larger the in-rush current it will draw when it has power again. This means that its bulk caps will be almost empty so the In-rush current could exceed the current handling capacity of the UPS and cause its shut down. This means that a PSU's hold-up time IS important!
  • turkey3_scratch
    Aris, you say the in-rush current could exceed the current handling of the UPS, don't you mean the PSU? And are you the Aris who wrote the article? Also, if the in-rush current exceeds the current handling capacitor of the bulk caps and the unit shuts down, will that cause hardware damage at all?