Creating long-lived specifications in a world of frequent technology changes
One of the greatest challenges facing Small Form Factor (SFF) industry trade groups is the creation of industry standards that leverage new technologies such as PCI Express while enabling a smooth transition from late life-cycle technologies such as ISA and PCI. But with new technologies churning rapidly, additional pressure is brought to bear as these standards must now anticipate further evolution and plan accordingly.
We’ve been fortunate in the SFF arena. Base technologies such as the ISA bus and RS-232 have enjoyed very long lives. This has allowed embedded systems designed to industry standards in the 1980s and 1990s to be refreshed with new components without changing the fundamental underlying architecture.
Today, system manufacturers in regulated industries require a bridge from earlier interface technologies (ISA and PCI) that allows their recently designed systems to take advantage of the new capabilities while retaining elements of earlier systems. This is particularly important when unique or custom components such as analog or digital I/O are fundamental to system implementation. SFF-SIG’s standards enable new technologies such as PCI Express and USB I/O expansion without forcing the obsolescence of popular long-life standards. For example, our new Stackable Unified Module Interconnect Technology – Industry Standard Module (SUMIT-ISM) Specification explicitly defines how to include a PC/104 (ISA) or PCI-104 (PCI) card within a SUMIT-ISM stack.
But the challenge is greater than simply providing a bridge to legacy interfaces. We know that PCI Express Gen 2 and even Gen 3 are right around the corner. So is USB 3.0. Upcoming changes in display interfaces will wreak havoc with system upgrades during the next decade. Even minor changes in chipsets and integrated processors from one generation to the next will cause difficulties with the number of ports supported or port configurations.
It is important that industry standards forming the bedrock of the SFF community have the ability to adopt new technologies that do not obsolete connectors and provide fully upward-compatible pin definitions. Frequent changes to standards that introduce a new connector or incompatible pin-out complicate upgrades, reduce the number of new products that adhere to the standard, and decrease options for all developers.
SFF-SIG is taking several steps to ensure that supported standards will continue to stay relevant for years, allowing further evolution to the new technologies described earlier. These steps include:
- Choosing connectors that have been proven to meet the performance requirements of PCI Express Gen 2 and Gen 3 and USB 3.0 (all specifications)
- Avoiding the inclusion of the graphics display interface du jour in the pin definition for SUMIT
- Accommodating reserved pins and a pin layout that enables a USB 3.0 definition, which requires more pins than USB 2.0, without obsoleting products built to the original specification (SUMIT, Computer On Module Interconnect Technology or COMIT, CoreExpress)
- Enabling a dual definition of the PCI Express x4 lane on the SUMIT interface to optionally support four additional PCI Express x1 lanes
- Offering a dual definition on display interface pins enabling a path to the new display port interface (CoreExpress)
- Supplying both 3.3 V and 5 V power input to minimize switching noise and conversion losses
- Providing multiple buses within a single low-pin-count connector to maximize connector life in the face of churning chipsets and flighty flash controllers (MiniBlade, SUMIT, COMIT, CoreExpress)
Taken together, these steps help provide reassurance that specifications developed by SFF-SIG will have the longest possible lifetimes, meaning that products that adhere to these specifications will remain viable solutions through the end of this new decade and beyond. SFF-SIG is well-positioned to incorporate next-generation technologies while remaining upward-compatible from the current set of standards.
That said, there are no guarantees. Our crystal balls reach only so far. However, it is also incumbent upon base technology developers to assure that their new developments provide for graceful evolution to the greatest extent possible. The responsible evolution of base technologies coupled with the steps taken by SFF-SIG allow embedded developers to incorporate products based around SUMIT, COMIT, Pico-ITXe, Pico-I/O, MiniBlade, and CoreExpress with a high comfort level that these products will attain maximum possible lifetimes.