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But PICMG specification allows for differentiation, too
After about a year and a half of work, the PCI Industrial Computer Manufacturers Group (PICMG) has completed its hot-swap spec for CompactPCI to allow boards to be inserted into or extracted from a system while that system is operating. Vendors have started to announce "hot-swap ready" boards and backplanes. But what, exactly, does that designation mean?
The answer is not clear-cut, because the CompactPCI hot-swap spec defines multiple levels of capability and complexity. While defining the "responsibilities of the platform [backplane] vendor, operating-system vendor and adapter-board vendor so hotswap boards will be interoperable across the full range of systems," the spec nevertheless "allows for differentiation by defining different levels of hot-swap capabilities for different feature/cost trade-offs," said Jeff Munch, chairman of PICMG's CPCI hotswap committee and director of engineering at the Monterey Design Center of Motorola Computer Group (MCG, Tempe, Ariz. ), formerly ProLog Corp.
The CPCI Hot Swap spec is primarily a hardware specification that points to the Hot Plug spec developed by the PCI Special Interest Group for its software component. Except for "a couple of registers," the software for a Hot Swap CPCI system and Hot Plug PCI system will be essentially the same, said Wayne Fischer, director of strategic programs at Force Computers (San Jose, Calif). Munch pointed out, however, that while "the lowest-level Hot Plug system drivers are platform-specific, we seek to accomplish platform independence for CompactPCI Hot Swap."
"Alternative hot-swap methods exist," said Kelly Ambriz, product marketing manager at PLX Technology Inc., "but they're proprietary, nonstandard approaches, and such custom solutions are too expensive to develop, manufacture and maintain."
On the hardware side, PCI Hot Plug and CPCI Hot Swap are very different. Hot Plug relies on motherboard circuitry for the live insertion or extraction of standard boards, while CPCI Hot Swap maintains a passive-backplane philosophy, relying on the addition of special circuitry to boards. Although Hot Swap does require that some changes be made to existing CPCI boards and backplanes, those items are being rolled into the core CPCI specification, said Jim Medeiros, manager of strategic programs at Ziatech Corp. (San Luis Obispo, Calif.). The goal is to have "all CompactPCI systems be hot-swap-capable for no cost."
The three...