GPU-Xpander Desktops are an economical way to enhance the Input/Output (I/O) power of any computer with an open PCIe x16 expansion slot. A hardware-only solution, GPU-Xpander expands the I/O capability of your computer by adding PCIe slots, power and cooling. Each Xpander Desktop model can add between two - four PCI Express slots to your computer, while using only one slot of the host computer. Add high-powered graphics GPU cards from NVIDIA for mathematical high-performance computing (HPC) or photorealistic 3D rendering to your existing computer with GPU-Xpander.

Our Experience

Recently, we were asked to install a Cubix Desktop Xpander to incorporate GeForce GTX TITAN Black Gaming Graphics Cards for a client, and thought we’d share the experience.

First off, the Cubix is a pretty cool box, and even cooler when you throw a pair of TITAN Blacks in there and turn the lights off.

Xpander Desktop


The Cubix Desktop Xpander runs off a PCIe card that is easily installed in the MacPro Tower, but there are some gotchas before we can get everyone singing together.

  1. The MacPro Towers will only see a maximum of 2 GPU cards in the Cubix Desktop Xpander – this appears to be a limitation in the BIOS of the MacPro Towers... so don’t buy 4 titans for your Mac and expect to see all of them!
  2. Minimum OS-X is Mavericks – we tried a couple of flavours, and had the most success using OS-X 10.9.4
  3. The Cuda and Nvidia Web Drivers were very specific – Nvidia Web Driver release 334.01.02, and Cuda version 6.0.51
  4. Internal GFX card choice is also important – we tried a K5000, K4000 and an old ATI Radeon – the K5000 was not able to see both titans simultaneously no matter what we tried (there may have been an update since our tests), the ATI appeared to see the titans with minimal effort, and the K4000 was our sweet spot once we had all the correct driver versions installed.

Now that everything was working, we threw in a Blackmagic Design DeckLink HD Extreme 3D, DaVinci Resolve 11, and fibre connectivity to the high speed storage.

Happy Times

After pulling back the old Resolve database, we opened it up and quickly set the preferences to use those Titans for GPU rendering and caching: Happy times and happy client!

Xpander Desktop

Unexpected Snag

On a side, we did hit an unexpected snag with Mavericks OS X and the Dell monitors in the client suite - Mavericks was not correctly seeing all the display resolutions of the clients dell monitor - we found a neat way to trick this was to install the DisplayVendorID-10ac edid files (from into /System/Library/Displays/Overrides/, and then hold the alt/option key when selecting the ‘scaled’ radio button in sys prefs -> displays - this brought up a larger selection of resolutions to choose from and we got the one we required straight away – no restart required.


I must admit being a bit sceptical after starting this project and hitting those roadblocks straight off the bat (we started with the K5000 as I had a spare one on my desk at the time), but once we knew the right combination, we started to appreciate the setup.

I hope this article helps others out there avoid troubleshooting the same issues we did.

Greg Taylor
Digistor Support Engineer