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What is I2O?

The article published below is part of a complete article from Michael Neuffer


Intelligent Input/Output (I2O) is a hardware specification that describes a model for offloading I/O processing from the CPU. There is no doubt that this is leading to extremely high performance I/O. The model is after the style of what has been used in very large mainframes for years. It is not a replacement for the PCI architecture.


First developed by a small group in Intel, I2O was extended to Microsoft and eventually lead to the creation of the I2O Special Interest Group. I2O does not introduce new concepts in I/O technology but is particularly attractive to companies related to the PC industry because it is designed to be cheap compared to large server solutions from IBM, SGI etc. I2O is also aimed at high-end workstations.


On their web site I2O SIG states "The I2O Specification is not only a technical work product of the SIG members, but an agreement about the intellectual content and the terms and conditions for how the Specification can be used. Therefore, to make the Specification available to non-members a non-disclosure agreement must be executed." This is why I2O cannot be called "open" in any sense.


Nevertheless there is some scope for Linux work. A draft copy of the specification has been (involuntarily?) distributed on the I2O SIG ftp site and has been helpfully mirrored at ftp.icemark.ch and landau.ucsd.edu.