Cooler Master GX 650W Power Supply Review

Cooler Master is breaking new maketing ground this time around with a "Gamer Xtreme" PSU at 650 watts. Marketing aside, it is packing a 52 amp single rail and a 5 year warranty, so maybe all is not lost on kitschy sales speak. Gag me with a spoon.



The Cooler Master GX 650W is just the 5th power supply we have seen from Cooler Master and so far in our testing Cooler Master has split evenly between good and, well, not good. Today's GX 650W is the first Cooler Master product we have seen in a while and is produced in conjunction with an OEM we have not seen Cooler Master use before, Seventeam. With a new product line targeting gamers and a new OEM provider how has Cooler Master done on this outing? Have they brought the batting average above .500? Or have they hit a foul ball today?

HardOCP's testing methodology is intended to very much push power supplies to their advertised wattage rating in temperatures that will represent some of the hottest computer enthusiast cases. So if a unit passes all our testing it is definitely not something to take lightly. In fact we expect more power supplies to fail our testing than make it through unscathed.

Build Quality

Kicking things off right today with our review of the Cooler Master GX 650W is probably not the unit's build quality. While the exterior of the unit is perfectly serviceable, it does have its shortcomings and it is not exactly a refined looking unit. The flat black paint job would be ok, if a bit low quality, if it was not also adorned with the giant orange-ish GX sticker and the housing lacked a wire guard. All in all, it is a cheesy look that is certainly meant to cash in on the whole "gamers like gaudy" mentality. Moving to the interior of the unit things don't get much better as we run right smack into an old style Seventeam group regulated design. Single layer PCB double forward group regulated designs haven't been high end designs in, well, years and today they really should be relegated to power supplies that cost a lot less than this unless they are somehow exceptionally superb (like the BFG LS 550W was). The overall integration of this unit is not horrible in all honesty. There are a few points of not the best soldering, and there are very few other corners cut from the design which at one time was likely a decent enough one. The component selection however could certainly use a bit of help as, among other things, this unit is filled out with Su'scon capacitors. However, at least the unit is covered by a 5 year warranty from Cooler Master, which will likely be helpful for owners and a liability for Cooler Master.

Load Testing

The load testing results for the Cooler Master GX 650W were so close to being a pass, but ultimately this unit could not overcome its antiquated design issues. Through the 120v testing today the unit survived but it posted mediocre voltage regulation, particularly on the 12v rail with its 0.45v drop over its tested loads. In addition to this, the unit posted some very dated efficiency values which range from 77.29% to 82.86%. This unit is supposed to be 80Plus certified, and is advertised as being up to 85% efficient. However, neither one of those things look to be very likely or perhaps while possible not to be expected, or even close, at realistic operating environments. When we moved into the 100v load testing things get a bit worse as during Test #4 the unit checked out for good. Through Test #3 though, we were seeing the same voltage regulation that we saw at 120v and the efficiency ranged from 79.64% to 81.82%. As the unit died during our regular load testing in never made it to our Torture Test, so how it would fare there for an extended period of time is still unknown.

However, we were able to carry out our Transient Load Test and in that regard this unit actually fits in with what we have seen from other units with similar topologies including the Seasonic M12II-620Bronze. The peak change on the loaded 12v rail was ~400mV while the peak change on the loaded 5v rail was ~140mV in both tests. These kinds of values are much worse on units of larger capacity as the transient load represents a much smaller portion of their total capacity than it does so with smaller units. So that fact, along with the performance of other similar units, makes this part of the Cooler Master GX 650W's load testing not only a pass but acceptable, not great but acceptable.

DC Output Quality

For those of you hanging on to the hope that the DC Output Quality of the Cooler Master GX 650W might redeem this unit, it won't. Right out of the gate the GX 650W was off on the wrong foot as all of the rails had traces of at least 20mV in amplitude with the 3.3v rail hitting 30mV or more than 1/2 of the ATX12v specification limit in Test #1. It should be no real surprise then that we find the 3.3v rail hitting the ATX12v specification limit of 50mV in Test #3 and then passing it on by as it hit ~65mV in Test #4. Sure the other rails did much better, with the 12v rail actually doing very well with its peak at ~25mV and the 5v rail peaking at ~20mV (though this is a greater percentage of the specification limit than 25mV is for the 12v rail), but that is all for not as the 3.3v rail did come undone and so the unit failed this portion of testing.


While the Cooler Master GX 650W has a number of features going for it that should allow it to be quiet, including a large 120mm overhead fan and a fairly uncluttered design, it was not nearly the quietest ~650W unit we have seen by a long shot. The majority of this issue I am going to have to speculate is due to the fan controller as this units fan ramped to some ridiculous noise levels (relatively speaking as this isn't exactly a Turbo-cool after all) without doing much in the way of awesome cooling ability. It was during Test #2 that the fan on the GX 650W became apparent, and from there it was off to the races. While there are likely older 80mm fan designs that are louder than this unit in the 650W range, it has been some time since we have had a 120mm fan that was as loud as this one. Certainly, much of that reason is due to the march of progress and the ramp in efficiency we have seen over the last few years. This GX 650W with its mediocre efficiency just can't seem to quite keep up with the heat and do so at what is now considered a quiet level. A few years ago, this likely would have been a different assessment, but time marches on.

Paul's Thoughts:

The Cooler Master GX 650W is the first Cooler Master power supply we have seen in a long time, and unfortunately it did not exactly leave me wanting more. Really it left me wanting some mouthwash to get this bad taste out of my mouth. The sad part is this unit is actually one I see a lot in retail and usually the price is over $100 (looking at you Microcenter) so when the opportunity arose to review this unit, I thought we might be on to something. A $100, 650W power supply can't be all bad right? Well I guess this unit isn't all bad but there were so many things about this unit that just scream "polished turd" in a box that it makes it kind of hard to see those things. The GX 650W at room temperature is possibly an ok unit barring the DC Output Quality. In the real world however, his unit is just simply half baked and it does nothing to help Cooler Master's brand in the power supply department. Why this product was launched is simply beyond me. Sure I can see segmenting your product with some different temperature ratings as the ATX12v specification does not dictate at what temperature the unit must function, but the ripple/noise values are fixed in the specification so there is no excuse for that failure from this unit today.

The Bottom Line

The Cooler Master GX 650W is a mediocre power supply for couple of years ago, and an outright failure today. The Build Quality of the unit is nothing to write home about (unless it is a warning), the topology is old and outdated, and the exterior is flash over substance. Coupled with this we have mediocre voltage, poor by today's standards efficiency, and out of specification DC Output Quality. One upping this poor showing is that fact that the unit was completely unable to complete our load tests at 100v AC input. That makes the GX 650W not just a failure by our standards, but rather a double failure and an ugly one at that. Making matters worse is the fact that this unit is priced at up to $100 in retail and $70 online. (Users can pick up the much better Seasonic M12II-620Bronze from Amazon with Free Prime Shipping for $98.29). As it stands, there really is not anyone that this unit would be a good fit for that we can think of, and certainly not for its intended crowd of "gamers." Cooler Master should be ashamed and owes all gamers and hardware enthusiasts an apology.

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