Review: OWC Helios Thunderbolt PCIe chassis with SSD

OWC Helios connects PCIe cards via Thunderbolt (December 14th, 2012)

MacNN Rating:


Product Manufacturer: Other World Computing

Price: $799 as tested

The Good

  • Robust construction
  • Supports daisy chain
  • Supports half-length PCIe cards
  • Fast SSD performance

The Bad

  • Relatively large
  • Expensive for SSD use
  • Requires AC adapter

As notebook computers become more powerful, and most all-in-ones now prioritize aesthetics over customizability, it is not uncommon to encounter difficulty when attempting to accomodate additional professional-level or out-of-the-ordinary hardware. Mac specialist Other World Computing is one of several companies that has come to the rescue, offering the Mercury Helios expansion chassis that connects a PCIe slot to a notebook or desktop computer via Thunderbolt. In our full review, we test the Helios bundled with a PCIe-connected 240GB solid-state drive.


The Helios chassis is purely utilitarian, housing the PCIe 2.0 slot in a black aluminum shell with ventilation holes covering the facade and backside. The large size provides space for any standard half-length PCIe card, measuring up to 6.5-inches, and an integrated cooling system with a variable-speed fan.

Two Thunderbolt ports enable the chassis to be used in a daisy-chain configuration with up to six devices. We tested the chassis connected directly to a Late 2011 15-inch MacBook Pro with a 2.2GHz i7 processor and 8GB of RAM, while a second trial placed the housing in the middle of a daisy chain alongside Apple's 27-inch Thunderbolt display.

Installing or swapping the PCIe card is easily accomplished with a Phillips PH2 screwdriver, which is the most common size. Construction appears to be robust--designed to withstand repeated swapping of cards, and an occasional bump during transportation.

The chassis is not gigantic, and it is lighter than some HDD storage systems, though the need for external power poses a limitation for true "portable" use.


OWC's SSD bundle includes the company's 240GB Mercury Accelsior PCIe drive, though the company offers alternative packages with SSD capacities ranging from 120GB up to 960GB.

Intech's QuickBench tests achieved maximum read speeds of 602MB/s during an extended test focusing on 20-100MB files, while write speeds neared 500MB/s in the same test. Switching to the benchmark software's standard hard-drive trial, the Accelsior speed topped out around 515MB/s, with sequential read/write and random read/write operations all running at more than 450MB/s for 1024KB files. The SSD performance was very impressive, and our results were comparable to OWC's own QuickBench achievements.

We did not find any difference in benchmark performance between the direct connection and a daisy-chain setup. This is not surprising, considering the Thunderbolt interface supports overall transfer rates up to 1250MB/s. Presumably a second or third SSD in the chain would be necessary to push Thunderbolt to its limit.

Final thoughts

The Helios housing and Accelsior drive enabled us to achieve data transfer rates as fast as an internally-mounted SSD connected via the 6Gb/s SATA 3.0 standard. If users are simply looking for external SSD storage, dedicated Thunderbolt drive enclosures typically cost much less--LaCie's Thunderbolt Little Big Disk is available with a 512GB SSD for $700.

Testing an SSD was an easy way to show the data throughput capabilities of a PCIe enclosure, however the Helios is better suited to alternative uses. It is perfect for users who need a PCIe card to help handle video editing/capture, audio recording systems and other specialized gear, all within a Thunderbolt chain that can be tied to newer MacBooks, iMacs and Mac Minis.

OWC currently sells the empty Helios chassis for $349, which is competitively priced against the $400 price tags found on Sonnet Technologies' Echo Express SE and mLogic's mLink.

by Justin King


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