One of the early examples of a “prosumer” product (that is, performing professional applications on a personal PC), Cooler Master’s original Cosmos PC case combined the advanced aesthetics of high-end workstations with the kind of deep feature set that high-end PC builders expect. The Cosmos series has persisted for enough years that some of its modern buyers probably won’t remember its earlier incarnations. That’s OK with us, as good looks and well-chosen features should both be timeless.

That legacy still looms large over the new $399.99 Cosmos Alpha—and Cooler Master clearly wants this latest version to feel like both a continuation and a statement piece. It’s bigger, bolder, and unapologetically premium in both presence and price. The design and feature set impress, and the interior is no-doubt flexible, with top or bottom power supply mounting, plenty of interior space, and practically limitless liquid-cooling mounting options. The actual building experience, in spots, proves less refined, with a few avoidable quirks. Still, it’s a hard-to-resist megatower that mostly lives up to its flagship ambitions. 

Design: It Handles Like It’s on Rails

The first thing you’ll see that sets apart the Cosmos Alpha from most big towers? Definitely the exterior rails, which resemble the gear-mounting racks on the roofs of some SUVs.

While the rails of the original Cosmos were designed primarily for appearance and/or panel protection, that’s no longer the case (cough) with its latest edition. With over an inch of space into which you can insert your mitts, the Alpha’s cast-aluminum rails add some height versus its early ancestor. The case is also about half an inch deeper and 2.5 inches wider than the original.

The Cosmos Alpha keeps the four Type-A ports of its progenitor but replaces its elder’s now-classic FireWire and eSATA ports with dual USB 3.2 Gen 2x2 Type-C. The original version’s USB 2.0 connections are upgraded to USB 3.2 Gen 1; the headphone and microphone jacks merged into a single four-pole headset jack; the power and reset buttons are moved to the outer rim; and an ARGB lighting mode button is added opposite the power button.

(Credit: Thomas Soderstrom)

The bottom panel’s dust filter slides out from the front, whereas the front panel’s dust filter is accessible by pulling the black grid section out of its silver frame.

(Credit: Thomas Soderstrom)

As the Cosmos Alpha has a large bottom radiator mount, the lower filter covers a similarly large area. Also notice that rubber strips are attached to the bottom edge of the lower rails to reduce scratching, sliding, and the transmission of vibration.

(Credit: Thomas Soderstrom)

The back of the Cosmos Alpha looks much like the front, so much so that the front panel’s grid fits there too, leaving only the rear panel’s lack of magnetic latches in the corresponding locations to prevent builders from swapping these. (Not that you would: The gaps above and below the smaller cover serve as cable passages.)

Also, notice that a giant perforated steel vent fills most of the right side’s panel.

(Credit: Thomas Soderstrom)

Speaking of perforated steel, the top panel pulls off to reveal a pair of adjustable fan rails, set wide enough to attach 200mm fans, with a hole long enough to fit two of those. The adjustability also helps if you want to install a 360mm-format radiator to align it however you like over the motherboard.

(Credit: Thomas Soderstrom)

Unlike the top panel, the front vent is all plastic: A flexible filter sheet snaps into place behind the rigid plastic façade.

(Credit: Thomas Soderstrom)

Lifting the glass panel from its hinges allows extra space for installation and removal of interior components, while popping out the front panel’s center section merely allows visual inspection of the Cosmos Alpha’s twin 200mm-by-38mm intake fans. Two identical power supply shrouds fill the gaps above and below the motherboard.

(Credit: Thomas Soderstrom)

I removed the power supply shrouds first to see how much space the case had (see the left image below), then removed the graphics card brace from the opening before going after the two cover panels on the inside (right-hand image). The hinges of both side panels are visible facing the back of the case.

(Credit: Thomas Soderstrom)

The Cosmos Alpha’s single rear fan fills one of the three fan mounts behind the motherboard and graphics card, limiting access to their rear ports. To the side, two crossbars that sit behind the motherboard tray can be fitted with additional cross braces to hold up to three 360mm radiators, but the only way to get room for all that hardware would be to move the motherboard tray out of the way, which we’ll get to momentarily.

(Credit: Thomas Soderstrom)

A third cable cover that sits behind the motherboard tray can be removed via two screws at the bottom to provide easy access to those cables. A removable triple-drive 3.5-inch/2.5-inch tray sits ahead of it, with an ARGB/PWM fan hub mounted to its center. For these two photos, I pointed the right side panel’s hinge perpendicular to its closed position.

(Credit: Thomas Soderstrom)

The Cosmos Alpha’s two factory-connected fans have no lighting; the two ARGB leads that appear in this photo are connected to the case's integrated light bars. I found that connecting the ARGB/PWM fan hub’s input cables to the test motherboard we use caused its front-panel mode button to be disabled, whereas pulling the ARGB lead from that motherboard allowed us to cycle the hub’s integrated controller through its 13 modes. Holding its button for a couple of seconds also turned the lighting off, but again only when the hub was operating from its own controller.

(Credit: Thomas Soderstrom)

Held in place by four sets of folding wing nuts and pinch brackets, the motherboard tray’s sliding adjuster allows users to expand the space behind the motherboard from 10mm to 80mm, though my test GeForce RTX 4070 Ti wouldn’t fit behind the glass panel when the motherboard was pushed to the extreme: The test hardware realistically allowed a bit over 60mm of maximum behind-motherboard space without buying the PCI Express riser cable needed to enable vertical card orientation in this case. (It’s not included.)

The curious will also notice one of the right side panel’s three hanger holes on the right hinge, as well as two of the four screws that hold the left hinge to the back of the case (left). My next image will bring this all together!

(Credit: Thomas Soderstrom)

Bounded at the top and bottom by a pair of full ATX-size power supply brackets, the eight-slot expansion panel and I/O shield join the motherboard tray as a sliding assembly that creates more or less space behind the motherboard tray for mounting additional cooling hardware.

(Credit: Thomas Soderstrom)

Building With the Cosmos Alpha

The Cosmos Alpha includes a user manual and a blizzard of packaged screw-and-connector hardware:

• 28 #6-32 combo-head screws
• 40 #6-32 panhead screws
• 12 plastic-engaging fan screws
• 12 33mm-long #6-32 screws for mounting fans to threaded holes
• A standoff socket, three motherboard standoffs, and a custom cooling tank standoff
• Eight M3 screws for mounting 2.5-inch drives/SSDs
• 10 zip ties and two self-adhesive cable ties

You also get two sets of rear fan brackets, a vertical graphics card mount adapter bracket, and two “GPU reinforcement pieces” that even the manual fails to properly describe.

(Credit: Thomas Soderstrom)

The Cosmos Alpha’s ARGB/PWM fan hub gets its PWM and RGB signals from the motherboard and its power from the power supply via an SATA power cable. Its front-panel connectors feature the usual nine-pin button/LED combo and HD Audio for the headset combo jack, plus two 19-pin USB 3.x header connectors for the four Type-A ports, and two Gen 2x2 leads for the Type-C ports.

(Credit: Thomas Soderstrom)

Since portions of the rear panel block access to the power supply’s mounting screws, Cooler Master made the Cosmos Alpha’s power supply brackets removable. Its screws are easily reached with all of the case’s external pieces installed, so all I had to do to start the test build was attach the power supply to it.

(Credit: Thomas Soderstrom)

You may have noticed that the Cosmos Alpha’s motherboard tray is more of a boxed section, and I noticed that it has holes at the bottom for passing cables…though not easily. A greater exception was found in the small center cable cover. (It covers the 24-pin ATX connector and is covered by a grid pattern; in the next image below, the AIO cooler hose passes over it.) It doesn’t stick out far enough to clear the case’s own Gen 2x2 USB cable when plugged into that header. Thus, the only way for me to use the cable cover was to forgo Type-C altogether.

The motherboard tray slid on its adjusters after I had already adjusted the graphics card brace, so I re-tightened the tray’s adjuster screws and re-adjusted the card brace, only to have the card brace’s threads strip. Adding a nut to the card brace finally got me moving forward again.

(Credit: Thomas Soderstrom)

Had I ditched the cable cover to access the test motherboard’s Gen 2x2 header, I’d still have been left with only one of the case’s Type-C ports working: My test motherboard didn’t have a second Type-E header connector for the case’s second Type-C port. Though NVMe-to-USB adapters like this one could feed the second Type-C port, my particular test motherboard uses a single heat spreader to cover all four of its PCIe 4.0 NVMe slots. You’ll have to look for a very particular motherboard with two 19-pin USB 3.0 headers for the four USB Type-A ports and two Type-E headers for the USB-C ports. Another option is an adapter that changes a USB 2.0 header to Type-E, if that’s your only board option, but that’ll slow down the connected Type-C port big-time.

The Cosmos Alpha looks stunning regardless of the hardware-specific issues I ran across, and I’m retaining the conflicting part to maintain the case’s as-designed airflow.

(Credit: Thomas Soderstrom)

Testing the Cooler Master Cosmos Alpha

Here’s a list of today’s build components, the standard test set I use for ATX builds...

Our build relies somewhat on fan proximity to cool things like the voltage regulator, so it’s no surprise to see an open-interior case like the Cosmos Alpha underperform slightly in thermal tests. On the other hand, the case provides the space you’d need to use even larger cooling devices, and more of them.

The Cosmos Alpha’s double-bent tempered side panel also does a pretty good job of deflecting internal component noise away from my SPL meter, and that’s something my ears can similarly appreciate.