Snap together Linux

Sandia’s Embedded Reasoning Institute has developed a small four-node Linux MiniCluster based on the small-sized PC/104 hardware.

Conducting research under the auspices of the Department of Energy, Sandia National Laboratories, a Lockheed Martin company, has built some of the world’s largest and most powerful supercomputing clusters in the world.

But big isn’t always better. So when Sandia’s Embedded Reasoning Institute, which specialises in machine intelligence applied to distributed embedded processor and sensor technologies, wanted to develop a small four-node Linux MiniCluster based on PC/104 hardware, it turned to Parvus Corporation to help out.

With four CPUs, a KVM switch for local diagnostics, 10baseT private network, and an external PCMCIA wireless connection, the resulting MiniCluster successfully demonstrates that Linux clusters can be portable as well as powerful.

The MiniCluster itself was entirely created out of commercial off-the-shelf (COTS) PC/104 compliant parts. Despite its small size (5.3′ x 5.3′ x 13′), it integrates all standard features of normal-sized rack-mounted clusters, including keyboard, video and mouse access to every node.

To form the units’ power base, Parvus combined an aluminium extrusion, end plate, 50W power supply module, and a PC/104+ Power Interface board which includes both PCI and ISA buses, dual fans and a thermal sensor to ventilate the bottom of the card stack.

The system’s CPU modules operate as Single Board Computers (SBCs) with the exception of the top CPU in the stack. Only the bottom three CPUs require power to be supplied via the ISA bus.

To interrupt all PC/104 bus lines except for the bus power lines and allow the high profile CPU boards to be connected together, double-height stack-through bus adapters are used to connect the four processors. These adapters help to solve PC/104 form factor height infringement.

Parvus’ left-loading PCMCIA Dual Interface provides a (wired or wireless) network interface on node 1 (top CPU in the stack) of the MiniCluster. This board uses the Intel (Cirrus Logic) PD6722 chip, which works well in Linux systems and accommodates Type I, Type II and Type III PCMCIA memory, I/O and ATA hard disk cards. All modules above Node 1 in the stack share a full PC/104 bus with Node 1. As hubs are required to expand a 10BaseT system beyond two nodes, two 10Mbit/sec Ethernet Hub boards are installed in the MiniCluster stack. Each offer four 10BaseT ports, one AUI port, and one 10Base2 (thin net) port.

One TP port on each hub module is used to interconnect the Hubs. Four others connect the CPUs on a private network and another is connected to an RJ-45 jack on the MiniCluster’s end plate to make the private network available to the outside world.

The hub board is based on the Level One LXT914 Ethernet repeater, enabling highly reliable communications, minimising issues with noise, cable deficiencies, and other network problems.

Integral to the MiniCluster stack is the PC/104 Quad CPU Switch, which serves as a Keyboard-Video-Mouse (KVM) switch to toggle between node functions. As it switches reset, speaker, and COM port lines between any of the four CPUs, the switch is used to perform local and diagnostic operations on the MiniCluster.

Input power applied to the board is jumper-selectable and may be routed from any single CPU system or the PC/104 bus. The I/O allows for either internal or external port selection. If intelligent control of the Quad CPU switch is desired, signals can be multiplexed under the control of a CPU or through an external rotary switch.

The MiniCluster incorporates SnapStik components to support the PC/104 modules in the stack. SnapStik is a series of snap-together board separators that create a low-cost, robust, incremental card cage for PC/104 boards. A threaded rod is inserted into each SnapStik corner and screwed into the power base with SnapMounts. The SnapStik assembly is tightened at the top by use of a SnapWrench applied to each of the top SnapNuts.

The SnapStik mounting system is more robust and easier to use than a solution based on traditional board standoffs, and yet in production quantities is comparable in cost. SnapGaps, SnapGuides, SnapMounts, and SnapSlots were all used in the MiniCluster design.

Parvus also manufactured a plastic 5X5 enclosure case, which slides over the top of the MiniCluster stack along each set of card cage’s SnapGuides to form a protective, yet clear shell.

In all, Sandia’s MiniCluster effectively demonstrates how a high performance computing environment can be quickly and inexpensively developed using PC/104 embedded solutions.

Such computers could potentially be employed in a wide variety of scientific and business applications, including weather prediction, human genome analysis, pharmaceutical design, aircraft and automobile design, seismic exploration, artificial intelligence, data mining, and financial analysis, among others.