What is PC104?
Rugged, Compact, Stackable and Modular

PC104 Definition
PC104 is an embedded computer standard defined by its compact footprint and its stacking bus structure. In essence, PC104 is a modular, ruggedized version of the PC. Instead of using a backplane, PC104 modules mate together via stackable ISA, PCI, and PCIe bus connectors. The stackable connectors and asymmetric corner mounting holes create a compact and modular rugged system.

PC104 leverages large PC hardware and software markets by following mainstream PC bus development. This reduces time-to-market, and minimizes development costs. Completely defined bus pinouts enable interchangeability and interoperability. This means that users and system designers can choose from a wide array of specialized PC104 modules to tailor a system to fit their project requirements.

The compact footprint of PC104, shown here on an SER25330
Octal-Serial Port module with a PCI/104-Express bus structure.

PC104 Benefits
The PC104 concept offers many advantages:

• Stackable: The design and location of the PC104 connectors (ISA, PCI, and PCIe) allow PC104 modules to be connected or stacked like building blocks. A PC104 stack might include a CPU (single board computer), a power supply module, and peripheral modules such as data collection modules, network modules, or storage devices. Modules within a PC104 stack are joined by stand-offs.
  
  
• Rugged: PC104 is inherently rugged. A small footprint and corner mounting holes ensure minimum PCB (printed circuit board) flex in high-vibration scenarios. Many modules are manufactured with extended temperature components, allowing operation from -40 to +85°C. Learn more about RTD's quality and process control.
  
  
• Compact: PC104 modules occupy a small footprint, but offer highly powerful computer processing and data-collection capabilities. Some applications might require one PC104 single board computer (SBC) and a power supply. Advanced applications can employ an SBC and multiple special-purpose peripheral modules such as GPS receivers, Ethernet switches, video controllers and data collection cards.
  
  
• Interoperable: PC104 modules are designed to work together. Users can tailor a system for their specific requirements using multiple PC104 modules from different PC104 manufacturers.

PC104 Bus Structures
The PC104 Specifications are based on a standard size, and a combination of PC buses. From the original PC/104 (ISA) to the latest PCIe/104 (PCI Express) the PC104 market offers a wide range of bus configurations:

Pictured Above (left to right): ISA, PCI, and PCI Express connectors.

PC104 Example Stack
The side-view diagram below shows the versatility of the PC104 bus structure variations. Here, the stack includes a variety of PC104 modules driven by PCI Express, PCI, and ISA buses. The interoperable PC104 standard allows users to take advantage of a huge selection of modules from dozens of PC104 manufacturers.

An example of a PC/104 stack incorporating multiple buses.

PC104 Specifications
The PC104 specifications are maintained by the PC/104 Consortium. Specifications for each PC104 bus structure can be found on the PC/104 Consortium website:

• PC/104 Specifications
• PC/104-Plus Specifications
• PCI-104 Specifications
• PCI/104-Express Specifications
• PCIe/104 Specifications

PC104 Deployed
PC104 systems are deployed in countless applications across the globe and in space. Because of its rugged design, PC104 systems are ideally suited for extreme environments where equipment failure is not an option.

The examples above show two different PC104 armored enclosure designs. On the left, RTD's HiDAN® offers a rugged, watertight PC104 stack housing with a wiring harness and military cylindrical connectors. On the right, RTD's HiDANplus® incorporates the same watertight rugged housing, but it also maintains the modular stackability of PC104. Learn more about RTD's rugged PC104 enclosure options.