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OWC Thunderbolt 3 Dock
Must-have expansion for iMac/MacBook Pro/Mac mini
Thunderbolt 3 • USB 3 • USB-C • Gigabit Ethernet • Dual Thunderbolt 3 Ports
4K Support • Mini Display Port • Analog sound in/out • Optical sound out
Works on any Mac with Thunderbolt 3

OWC Mercury Helios Thunderbolt Expansion Chassis for PCIe Cards

Want to expand your MacBook Pro with a PCIe card or large SSD?

OWC’s Mercury Helios Thunderbolt Expansion Chassis accepts a PCIe card and connects to any Mac with a Thunderbolt port.

OWC Mercury Helios PCIe Thunderbolt Expansion Chassis

The Helios chassis is available empty (install your own PCIe card), or bundled with an OWC 480GB Mercury Accelsior PCIe SSD up to 960GB (see review). You can also install any other PCIe card in it. Units can be daisy-chained for more than one card.

This is a very nice option to have for an otherwise un-expandable MacBook Pro and MacBook Pro with Retina display. My only complaint is that the fan is louder than I like, so I stuck it under my desk, which helps.


I observed the following commendable behavior:

  • No drivers needed.
  • The Accelsior in the Helios is fully bootable, including the OS X Mountain Lion recovery partition.
  • The Helios enclosure sleeps when the computer is put to sleep— it powers off as does its fan.
Up to 1527MB/s sustained performance

Real World — Photoshop CS6 scratch volume

You can waste your time reading silly benchmark geek/nerd tests. Or you can put hardware to work and see how it performs on a real task— for me that means Photoshop.

To stress the disk speed end of the equation in order to compare the performance of the internal Apple 512GB SSD against the Helios + Accelsior, I ran the diglloydHuge benchmark , which requires about 56GB of working space. Since a 2012 MacBook Pro maxes-out at 16GB of memory, this exercises the Photoshop scratch disk heavily.

As the graph shows, the OWC Helios + Mercury Accelsior combination handily outperforms the internal Apple 512GB SSD by a very large margin; the Apple SSD took 41% longer to complete the task.

Photoshop CS6 — diglloydHuge benchmark, time in seconds (lower is faster)

Sustained transfer speed

DiskTester was used for this test, specifically the fill-volume test.

Shown below is speed as tested using the OWC 480GB Mercury Accelsior PCIe SSD in the OWC Mercury Helios enclosure on the MacBook Pro Retina.

This speed with compressible data exceeds what is possible with the internal Apple SSD. Compressible data is a bit slower for writes, but still very fast. Real world performance is what matters anyway; see the Photoshop CS6 results above.

Sustained transfer speed
OWC Mercury Helios PCIe Thunderbolt Expansion Chassis + OWC 480GB Mercury Accelsior PCIe SSD


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