Corsair Obsidian 900D vs. Cooler Master Cosmos II

Josh Norem

Corsair Obsidian 900D vs. Cooler Master Cosmos II

The Cooler Master Cosmos II debuted in 2011 to much fanfare. Indeed, it was the chassis of our dreams. It housed our precious Dream Machine that year , and was easily the best “super-tower” available. In 2013, the Corsair 900D came on the scene boasting a similarly mammoth stature, and was itself chosen for Dream Machine 2013 duty due to its water-friendly nature and towering physique. Both cases represent the pinnacle of PC case design, so they must do battle.

Corsair’s new Obsidian 900D “super-tower” is tall and roomy, but much less beefy than the Cosmos II.


Size and Weight

Both cases are big, but it’s how they carry their bulk that makes all the difference. The Cosmos II weighs 48 pounds, while the 900D weighs 41 pounds. The Cosmos II is 27.7 inches tall while the 900D is 27.2 inches, so the two are very close in size. To be honest, we originally felt that the Cosmos II was too heavy because it’s built like a tank. Then we lifted the Corsair 900D out of its box and were a bit let down by its relatively light weight. It just feels too lithe for a case of its size, and there’s no easy way to move it, whereas the Cosmos II has built-in handles, which makes transport much easier. Therefore, we give the Cosmos II the nod, because we wish the 900D had a bit more heft to it and an easier way to move it than squat and grunt.

Winner: Cosmos II


Total Capacity

It’s safe to say you’d need to have a drug cartel’s bankroll to ever outgrow either of these cases, but it’s still important to gauge overall capacity. For starters, the Cosmos II has 13 3.5-inch drive bays compared to the 900D’s nine bays, though you can buy two more three-drive cages for a total of 15. The 900D has one additional 5.25-inch drive bay to its credit—four total. Both cases hold ATX and E-ATX mobos, as well as smaller boards, but the Cosmos II holds several larger variants, such as XL-ATX, SSI CEB, and SSE EEB. The Corsair 900D has room for dual PSUs, however, mounted vertically, whereas the Cosmos II can hold only one. Both cases have more than enough room for any combo of GPUs your bank account can tolerate. Since both cases are very evenly matched in this category, and can easily swallow even a Dream Machine, with room to spare, this one is a tie.

Winner: Tie


Build Quality

When you drop $350 smackaroos on a chassis, you expect top-notch build quality, and unfortunately only one of these cases lives up to that expectation, and that’s the Cosmos II. Though both cases are made with a steel frame and feel extremely solid, the fit and finish of the Cosmos II seems much more polished than that of the 900D. With the Cosmos II, everything that moves glides smoothly, doors and latches lock into place tight and secure, and you never get the feeling that any part of the case is brittle or untrustworthy. The 900D, however, has two glaring weak spots—its disappointingly flimsy lower bay doors, and it’s flaccid 3.5-inch drive-bay assemblies. Both of these rickety contraptions feel out of place on a chassis of this class, and require too much fumbling for our well-heeled tastes. The lower drive-bay doors are surprisingly wobbly, with a magnetic retention mechanism that barely works.

Winner: Cosmos II


Cooling Options

If you’re running air-cooling, both of these cases provide more mounting locations than you can shake a heatsink at, though they are modestly outfitted out of the box with just a handful of 120mm spinners. When it comes to liquid-cooling opportunities, though, the Corsair 900D is the clear winner, providing ample radiator mounting options on almost every surface of its spacious interior. Not only can you mount a 480mm radiator on the top and the bottom, you can put a 360mm rad in the front too, or two of them in the bottom if you’re cray cray. The Cosmos II can handle a 360mm up top but there is no way to mount a radiator to the front of the chassis. You can also mount just a single 240mm rad down below due to the PSU’s horizontal orientation, plus the Cooler Master provides mounting rails for only one radiator.

Winner: Corsair 900D



Cases such as these are not mere storage containers, but rather canvases that allow you to express your inner geek via expansion, modification, and customization. To that end, both cases are fairly modular, allowing you to remove fans and drive cages to install cooling components or to manage cables. The Corsair 900D lets you remove and rearrange pretty much everything, including the lower and upper drive bays as well as the PSU location. The Cosmos II, on the other hand, offers fewer options due to the PSU’s location and the steel shelf that divides the chassis’s lower quadrant. You can still remove the upper and lower drive cages, but your options for moving the drive cages around are limited. You also can’t change the location of the power supply, nor can you add a second one if you need to, which is a situation we confronted while building this year’s Dream Machine.

Winner: Corsair 900D

The Cosmos II is one of the largest cases ever made, and has a shipping weight of 50 pounds.

And the Winner Is…

As we come to the finish line both cases are tied, so the winner is not immediately apparent. After searching our souls, examining our PC fantasy builds, and consulting with our shaman we arrived at a winner—the Corsair 900D . It’s the winner for one simple reason: It offers more flexibility for ambitious builders who want the option to expand their builds in the future, including running liquid-cooling, for which it’s the best case around, period.

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