Slots, slots, and more slots has long been the cry of industrial and commercial users since the advent of the PC. Slots provide the ability to add specialized cards that perform application functions that the PC or Mac  Workstation don’t have. In fact, the Mac Pro Workstation only provides one PCIex16 and two PCIe x4 Gen2 slots. Laptops offer even a greater challenge if you want to add application boards because they don’t provide any extra slots. So if you want to add a fast storage Flash board, RAID card, 10Gb Ethernet card or anything else that your system doesn’t have on-board, you’ll need something outside the box.  Enter the expansion enclosure.

A number of types of expansion have become available for both system-to-IO and systems-to-system communication. Ethernet has dominated the systems-to-system world for a number of years. USB, Fiber Channel, Firewire, Infiniband, Rapid IO, and others have been invented to support IO expansion.  PCI Express (PCIe) over cable and Thunderbolt are the latest to capture a share of the system-to-IO market. 

The performance graph above illustrates the difference in bandwidth between the popular types of expansion.

As laptops become more powerful, they are used in more and more applications where mobility of the system is required. The only problem is the limitation of adding necessary boards to the system. This is especially noted in applications like film capture on location or industrial control or system monitoring or any application where special boards are required. The proliferation of add-in cards today makes it easier to add cards to a PC or MAC workstation but what about a laptop? Expansion has become the answer for some IO obstacles like data storage that can be connected to the laptop or workstation through USB and Fiber Channel and Ethernet is used to connect multiple PCs. But even USB3 only operates at 5Gb/s. Thunderbolt doubles that with a 10Gb/s bandwidth plus a 10Gb/s display port bandwidth. ExpressCards with PCIe cable adapters are available to add expansion to laptops but only 2.5Gb/s bandwidth is brought out through the ExpressCard slot on most laptops. And the ExpressCard slot has been eliminated on many laptops today.  This makes Thunderbolt the best option for adding expansion to laptops.PCIe expansion was developed in 2006 and has experienced a slow adoption in the rackmount and embedded computing market. Recently this high speed expansion has entered the commercial market to support expansion enclosures for IO boards and disk arrays. As the performance chart indicates, PCIe connectivity packages are categorized by the number of traffic lanes that are supported where in Gen1, one lane operates at 2.5Gb/s, Gen2 at 5Gb/s and Gen3 at 8Gb/s. While PCIe x1 Gen2 is comparable to USB3 in theoretical bandwidth, conversion from PCIe on the motherboard to USB is required which slows the speed of the data from the motherboard to the IO card. Since PCIe is the same bus that’s on the motherboard, there is no conversion and thus much less latency. PCIe expansion is ideal for imaging, film editing, graphics and any application requiring high speed data transmission.

Several Thunderbolt and PCIe expansion enclosures have recently been introduced to the market. The mCUBE from One Stop Systems (OSS) adds functionality and performance to your system and does it less expensive with a lighter, quieter, and more attractive system than anything on the market today. 


While Thunderbolt has received a lot of ‘air time’ recently, as the performance graph illustrates, it’s far from the fastest expansion bus available. That nod goes to PCI Express. Today’s high-end GPUs operating at Gen3 speeds of up to 128Gb/s, require the PCIe Gen3 bus to support them.  Many of the PC’s or MAC workstations today may only have one or two PCIe x16 Gen3 slots and even then the PC’s may not have the power or cooling to support them. This is an ideal application for an expansion enclosure that can support a number of GPUs along with other additional cards. A 3D rendering application with multiple monitors can operate at a much faster rate with multiple GPU’s.

                The PCIe connectivity package includes a PCIe cable and a host cable adapter. Simply remove the cover of the workstation and install the cable adapter in the available PCIe x16 slot. Plug the PCIe cable into the cable connector on the adapter card and into the expansion enclosure that houses the cards. The expansion chassis typically powers up automatically when the host system is turned on. Sometimes there may be an on switch on the expansion chassis that is switched on after the host powers up. The only software that needs to be added is any drivers required by the individual cards.

                Mobility is a huge advantage of expansion chassis. Smaller and lighter than a workstation, an expansion chassis and laptop can quickly become mobile. The film industry, along with many others, uses laptops to download digital images and video on location. High-end digital cameras use software and boards to accelerate the download and transcode time from the cameras. These boards along with Flash memory boards for fast storage can be installed in the enclosure and simply plugged into the laptop when required.

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