is 650w psu is enough for sli gtx 670

Conclusions
The Cooler Master GXII 650W is just the 8th power supply we have seen from Cooler Master and is the direct successor to the GX 650W. Previously in our testing, Cooler Master power supplies have been split between good and not so good power supplies with the GX 650W being just outright bad. With a new OEM provider for the 650W model in the GXII line, has Cooler Master made a 180 degree turn for the GX lineage and posted good results like their V-Series has been doing? Or is Cooler Master continuing in a 360 degree turn around the toilet bowl with this lineage?

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
First things first today, the Cooler Master GXII 650W sets off on the wrong foot and breaks an ankle at the starting gate with the build quality. As with the GX 650W before it, the exterior of the unit is perfectly serviceable but it does have its shortcomings and it is not exactly a refined looking unit. Among those things are the giant garish orange-ish GXII sticker and the housing lacked a wire guard. On the plus side, the new GXII 650W does have a nicer fan grill than the GX before it. Moving to the interior of the unit, things don't get any better as we run right into an old group regulated design once more, this time from Enhance. On top of that, this unit features a single layer PCB and, when we flip that PCB over, we find a train wreck where Enhance (who usually does much better than this) has kludged a dual layer PCB design onto a single layer PCB. The PCB work and soldering is just awful making the overall integration of this unit horrible. Adding insult to injury, the component selection is bad as well. Indeed, the capacitors are provided by Teapo and Taicon which is not good to see and the fan that is in this unit is not the one that is advertised on the packaging. There are just so many things wrong to start with on this unit that it’s a good thing that the unit is covered by a 5 year warranty from Cooler Master.

Load Testing
As will become somewhat of a recurring theme today, the load testing results for the Cooler Master GXII 650W were very similar to what we saw with thee GX 650W and that means ultimately failing. During the 120v load testing, which is the only portion that this unit would finish, the GXII 650W saw kind of mediocre voltage regulation that ended mixed compared to the previous GX 650W. Indeed, the 12v rail only dropped 0.27v this time but the minor rails both dropped by 0.09v which is, by percentage, worse than the 12v rail and worse than what we saw with the GX 650W. In the 100v load tests, we see some slightly different output voltages but ultimately the unit died during Test #4 so the unit failed testing. Also, as it was dead and all, it was unable to do the Torture Test at all. While living though, it posted efficiency values which ranged from 81.16% to 87.11% at 120v and 83.01% to 85.82% at 100v which are better than the GX 650W. That all said, due to the failure, this unit ends up in a gutter-esque three way tie with the GX 650W and OCZ ZT650 while being bested by the recent XFX ProSeries 650W and the Enermax Triathlor 650W. In the 80 Plus testing, this unit finished testing with efficiency values of 84.86%-86.32%-81.20% which means that it missed the 80 Plus Bronze cutoffs at full load by about 0.8%. Lastly, before moving on, the voltage regulation on the minor rails in the 80 Plus test was just awful. If for whatever reason you buy this unit, be sure you don't have any serious draw on the 5v or 3.3v rails.

In a blazing awesome show of mediocrity, the Cooler Master GXII 650W manages to end up mixed compared to the very marginal Transient Load Test results we have seen from all of the recent 650W 80 Plus Bronze power supplies. The peak change on the loaded 12v rail was ~330mV while the peak change on the loaded 5v rail was ~230mV in both tests. Sure, these kinds of values are much worse on units of larger capacity as the transient load represents a much smaller portion of the total capacity than it does on smaller units such as this, but this unit did hit the ATX12v specification limit and it could not improve overall on its three year old predecessor. So, while not failing and firmly mediocre, at least this unit has moved up to compare with the competition.

DC Output Quality
In the DC Output Quality portion of testing, we see the GXII 650W making some strides over the previous GX 650W. Indeed, this unit starts off testing in better shape than the GX 650W and it finished with peak trace amplitudes of ~40mV on the 12v rail, ~25mV on the 5v rail, and ~20mV on the 3.3v rail. Now, before you go and celebrate this improvement, it is important to note that the GX 650W was a flaming pile of crap in this aspect of testing last time as it completely went out of specification. It's easy to hurdle a bar when it is that low. On top of that, while absolutely better, relatively this unit is bringing up the rear of the recent comparable 650W units as it trails the Enermax Triathlor 650W and the XFX ProSeries 650W. So, while not an absolute pile of crap like its predecessor, the GXII 650W is still looking up and seeing a lot of dog butt from the back of the pack of comparable units we have seen in this aspect.

Noise
While the Cooler Master GXII 650W has a number of features going for it that should allow it to be quiet like the GX 650W before it, and it even has better efficiency than that unit, it was not the quietest ~650W unit we have seen. It does, however do better than the GX 650W; again a low bar to hurdle. While the GX 650W roared to life early in testing, the GXII 650W was much calmer with its fan ramp seeming to only start really aggressively during Test #3 at 100v and continue from there until the unit died in Test #4 at 100v. Even when at full ramp, this unit was not stunningly loud but more than loud enough to let you know that the fan was there and the fan was working. Perhaps if this unit had come equipped with the HDB fan it was advertised as having it may have been quieter, though sleeve bearing fans generally are relatively quiet. Then again, it probably would still be a dead power supply with a HDB fan instead of a dead power supply with a cheaper sleeve bearing fan. So......

Paul's Thoughts:

The Cooler Master GXII 650W is somewhat of a weird duck to me due to the conundrum it represents. To start things off with, it is better than the old GX 650W if for no other reason than it failed fewer portions of testing than the GX 650W did. On the flipside, the build quality is a wreck and probably a step backwards compared to the GX 650W with that horrible should have been a double layer PCB and the wrong fan in the unit. This unit is not an entry level product it is a "gaming" product along with the V-Series units which is slotting in ABOVE Cooler Master's Office/Home options. So, to have a unit that is this poor aimed at the crowd that is MOST likely to actually really push a power supply to the limits seems just bizarre. I mean, a passing 650W unit is not a stretch to produce in this day and age even at a low entry level price point (wait this thing is $89.99 at Amazon? This unit should work and it should be doing better than the previous GX 650W. I guess that maybe there is just a lack of caring about this product at Cooler Master since this isn’t a flagship product and this isn’t a small manufacturing blip that was missed on this unit. There was seemingly no oversight at all during the conception and production of this unit given the laundry list of issues that we see today. Sure the GXII 650W may work at room temperature (poorly I might add, just look at the 80 Plus voltage regulation), but all that leaves you with today is a luke warm turd and I think Cooler Master wants to be aiming a bit higher than that these days. And thankfully it seems to once again be on somewhat of an upward path.

The Bottom Line
The Cooler Master GXII 650W is another example of a mediocre warmed over power supply from a number of years ago being pushed out to consumers today like chicken that has been sitting out on the counter-top under warming lights too long. If that sounds familiar that is because this unit’s predecessor, the GX 650W, was much the same kind of failing product. Indeed, this unit takes just about every page out of the original GX 650W's book and uses that as a template of where to start to go wrong. The build quality of the GXII 650W is probably worse than what we saw with the GX 650W due in no small part to the amount of corners cut including the PCB work, the wrong fan, the quality of the other components selected, and the old/outdated topology. Somewhat unsurprisingly then, or maybe surprising that it wasn’t worse, we find mediocre voltage regulation when the unit would run. We find OK but unremarkable DC Output Quality, and efficiency that misses the 80 Plus mark by a touch. It is important to remember that we have to frame all of those summaries of its performance inside of the caveat of "when this unit would run" as that was not always the case since it failed in our load tests at full load 100v input just like the GX 650W. With a price of $90 in retail, Cooler Master sure seems proud of this unit, too bad that pride did not show in the product quality in addition to the price point.

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