What is XR-DIMM™?

XR-DIMM™ is a new multi-sourced rugged memory module standard for the embedded systems market. XR-DIMM™ was originally announced as RS-DIMM, but the name has been changed to emphasize the eXtreme Rugged aspects. The specification defines both unbuffered and registered versions which are analogous to their SO-DIMM counterparts. The module is narrower than the SO-DIMM module, allowing it to fit better on narrow processor boards and modules. In addition, the module can be secured with two screws to better resist shock and vibration. Finally, the optional SATA pins allow SBC and COM manufacturers to reduce space consumed by connectors on their products.

Specification

XR-DIMM™ 2.0 Specification (1.54MB PDF)

Backgrounder: What is XR-DIMM™?

Fact Sheet for XR-DIMM™?

FAQ (Frequently Asked Questions) about XR-DIMM™?

Press Release

FAQ

A low cost logo licensing agreement for non-members is under discussion.

  1. What is SFF-SIG's XR-DIMM™ rugged memory module?
  2. Why do we need another memory standard?
  3. How has the ruggedness been confirmed?
  4. Is XR-DIMM™ compatible with current JEDEC memory devices?
  5. Who is supplying XR-DIMM™ memory modules?

What is SFF-SIG's XR-DIMM™ rugged memory module?   Top
The XR-DIMM (eXtreme Rugged - Dual In-line Memory Module”) Rugged Memory is a small form factor (38 x 67.5 mm) mezzanine DDR3 expansion memory module for use in embedded applications requiring exceptional resistance to shock and vibration as well as extended temperature operation. XR-DIMM™ was originally announced as RS-DIMM, but the name has been changed to emphasize the eXtreme Rugged aspects. The XR-DIMM pin definition closely resembles the DDR3 SO-DIMM pin definition to ease the implementation of CPU designs which may wish to utilize both expansion memory approaches for differing types of applications. The XR-DIMM pin definition also includes a SATA interface to enable the development of dual function modules containing both DDR3 memory and flash memory for a Solid State Disk (SSD) implementation.

Why do we need another memory standard?   Top
For years, designers of off-the-shelf embedded CPU boards (both SBCs and COMs) for use in rugged applications with significant resistance to shock and vibration have been faced with difficult design decisions for their main memory. Standard memory expansion interfaces such as DIMM and SODIMM memory are not designed for these rugged applications. Therefore, significant concern exists about the use of such standard memory expansion approaches including the very thin gold plating that can be rubbed off by the memory socket pins. The XR-DIMM approach provides for off-the-shelf, commercially available eXtreme Rugged memory expansion modules of varying capacities, allowing the CPU manufacturer to offer multiple memory size solutions to the OEM customer while maintaining a single CPU SKU. Space on the CPU board is limited to the connector and mounting hole locations. And upgrading memory capacity is as simple as swapping memory modules. Enhanced ruggedness is obtained through the use of a high performance 240-pin socket connector system and the use of standoffs with screw attachment firmly holding the CPU and memory module together.

How has the ruggedness been confirmed?   Top
Initial products built to this specification have been tested to ANSI/VITA 47-2005 for both shock and vibration.

Is XR-DIMM™ compatible with current JEDEC memory devices?   Top
Not per se. To achieve ruggedness, a pin-and-socket connector system is used, similar to that use with various COM CPUs. However, the pin definition closely follows the SO-DIMM pin definition, albeit with more pins, so that a CPU originally designed with an SO-DIMM can be easily adapted to XR-DIMM operation.

Who is supplying XR-DIMM™ memory modules?   Top
Several embedded-focused memory manufacturers have built products, including SMART Modular, Swissbit and Virtium.



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