The MXC Form Factor

Figure 3. Viewed from the bottom, the MXC card offers a sturdy 500-pin Samtec Searay connector that minimizes footprint while allowing 10-Gbps signaling.
The most fundamental MXC characteristic is its size: it’s small enough to fit two modules on a 3U-sized card and four can fit on a 6U card. This isn’t simply a matter of outer dimensions, since at 85x70mm for a Type A card, it would appear to be similar in size to an 82x70mm Type A MXM 3.0 card. The difference is the connector arrangement: the few extra millimeters required by the MXM card edge connector makes it impossible to fit two on a 3U card (or four on a 6U card).

The next obvious characteristic of the MXC form factor is the sheer number of pins — 500. The pin arrangement is shown in Figure 1, and it is specifically geared for graphics and video applications. Banks of signals are available for analog or digital video in and out channels and can be configured for RS170, RGB, DP, DVI, TMDS, LVDS and SMPTE (SD-SDI to 3G-SDI) video formats. Together, as many as four different video input signals can be mixed and overlaid on up to eight different video outputs.

Video output data can be simultaneously compressed, encrypted and delivered through USB 3.0, PCIe or Ethernet 10/100/1G/10G connections. VPX carriers or baseboard-level systems using multiple MXC modules can communicate using 16 lanes of switched PCIe 2.1 or separate video interconnect busses, drastically reducing the effort required to interface video data sources that weren’t necessarily designed to talk to each other.

Figure 4. The MXC module seen from above, and with the heat shield shown detached from the board it protects. The heat shield allows the use of reliable conduction cooling techniques.
On 3U VPX/MXC carrier boards, 32 PCIe lanes switch between the two MXC modules, enabling them to DMA each other or to communicate to the backplane. This makes it possible to create high-performance multi-board system solutions (Figure 2). Four modules on a 6U card can work together on a sophisticated display algorithm using the bandwidth of 96 switched PCIe lanes. This PCIe interconnect provides a highspeed, efficient, standard way of moving data at 80 Gbps for 3U VPX/MXC carriers and 160 Gbps for 6U VPX/MXC carriers.

The achievable signaling speeds are drastically affected by the quality of the connector, visible in Figure 3. Video signals may need to travel at over 3 Gbps; the so-called Generation 2 PCIe revision has doubled the original PCIe rate to 5 GT/s (Gigatransfers/ second, equating to 5 Gbps for a single lane), and it is anticipated that this speed will increase with future generations of PCIe. Because the MXC card uses a Samtec Searay connector, it can handle up to 10-Gbps signaling, providing headroom for today’s speeds and extending the useful lifetime of the card as signaling speeds increase in the future.