Equipment

The Box

Basically throw away the Akitio chassis but keep the  power cord from the transformer to the chassis (the DC power part).  We will use the cord later.  I built a plexiglass box to hold all the components and made it large enough to put the beefy power supply and two GPUs.  Extra room in a prototype generally turns out to be prudent.  The acrylic just lying around happens to be from US Plastic and is pretty close to Nvidia ™ green.  Rough measurements: 12in x 12in x 7.5 in.  Five sides are acrylic cemented together with the sixth side (top) is screwed into the left and right sides with 4x 1.3mm wood screws.

Assembly

The GPU plugs into the Akitio board via PCIe, PC power supply powers the GPU via 8-pin and 6-pin PCIe molex connectors, the power supply’s ATX connector goes into the SWEX, and rocker switch connects with two pins to the SWEX. Easy.  The fun part is powering the Akitio board off the PC power supply.  We saved the Akitio DC power cord, so stripping that back and soldering in a HDD 4-pin molex power connector using the GND and +12V (yellow) wire gives us the “adapter” we need.  Behold the ASCII! (all connections are power related unless specified):

The Prototype

Front View Rear view Side view (with PC power supply and SWEX) Side view (with PCIe-thunderbolt2 board and GPU)

References:

http://forums.macrumors.com/threads/diy-egpu-for-mac-mini-2012-osx.1772495/