RTC Magazine

In many military, government and private industry situations there is a need to display large amounts of dynamic data so numerous people can collaboratively view, analyze and respond to it. The amount of data involved in such an operation can be substantial and often will not fit in a window on a desktop display or even on the entire display. The data to be displayed may include numbers, charts, graphics, video signals, satellite images, weather maps and sometimes even the entire desktop displays of one or more users.

This data must be updated frequently. Live video must look like it’s live, and application programs must respond to user input as fast as a desktop computer would. This places incredible demands for bandwidth on any system designed to handle these disparate data sources in an integrated manner. To provide the needed display, wall projectors with 1-2 million pixels resolution each are assembled into a tiled array creating a wall that can be used as a shared display. The projectors are driven by a display wall controller so the entire display surface can be treated as a single logical display.

These controllers are basically powerful computers with the ability to drive multiple outputs and to capture and display both video and high-resolution RGB signals. The advantage to this integrated approach is that video and RGB signals appear in windows, just like application programs, and can be resized and moved anywhere on the display wall. But as modern demands for data increase, the size and capabilities of the video wall must increase. Here’s how Jupiter Systems migrated a PCI-based controller system to one linked by PICMG 2.17 and the serial scheme StarFabric, and in the process realized an order of magnitude increase in performance, with lots of capability headroom.

Typical Application Environment

Figure 1 shows a modern electric utility control room. This center, installed by HB Communications of North Haven, Connecticut, contains three display walls and numerous operator consoles. Each display wall consists of eight rear-projection cubes and provides over 10 million pixels of display space. In addition to running local and networked applications on the wall, up to 16 video signals and eight high-resolution RGB signals can also be displayed.

Display walls are usually fixed installations, but they can also be small and portable. Figure 2 shows such a system with three front projectors mounted on overhead struts in a military tent setting. This tactical operations center (TOC) configuration can be set up in one hour and taken down in half that time.

Existing System Architecture

The goal was to create a next-generation controller architecture that would support more output displays, higher resolution per display and multiple live video overlays. In addition, the entire configuration needed to be scalable to as-yet-undefined configurations. In 2002 Jupiter’s display wall controllers, the Fusion 930, Fusion 950 and Fusion 970 were based on the 32-bit/33 MHz PCI bus (in a CompactPCI form-factor in the Fusion 970).

The 32-bit/33 MHz PCI bus provides 1 Gbit/s of bandwidth for CPU access to the graphics controllers and for peer-to-peer communication between the various devices on the bus. This bandwidth wouldn’t have been a problem if CPU activity were the only traffic on the bus, but the bus is also used for pixel traffic for some video signals and all of the captured RGB signals that are displayed on the wall.

The amount of bus bandwidth required to update a window containing a captured RGB signal is substantial; an SXGA signal is 1280x1024 resolution, or 1.3 Mpixels. Using 16-bit color depth and a thirty frame per second update rate requires 600 Mbits/s of bus bandwidth, about 60% of the theoretical PCI limit. Attempting to handle multiple signals at that update rate isn’t going to work. In an ideal and static world, the bus could be segmented to localize such traffic, but in the real world that isn’t feasible. It was apparent that the current architecture had reached its performance zenith, and that further demands would result in inadequate graphics performance and impinge on the very purpose of the display wall.