I2O

Intelligent Input/Output, better known as just I2O is a computer Input/Output specification primarily used in servers and high end storage controllers, it was originally designed to allow PC servers to offload I/O from the main processor much in the same way that mainframes do. I2O was originally designed by Intel and made use of a their i960 RISC processor as the offload engine, in 1996 the company formed an industry group called "I2O Special Interest Group" that took over the development of the technology and publishing of the specifications.

I2O uses a split device driver model that has an "OS Module" running on the host system and a "Hardware Device Module" running on the I/O processor that used message passing for communications, thereby giving the system a degree of hardware driver independance. The I2O driver model conforms to platform neutral device driver interface standard known as Uniform Driver Interface (UDI) that Intel developed in a similar timeframe.

I2O was quite popular for a while amongst server manufacturers and there is still support and new hardware available for the standard in some modern high end x86 servers as of 2016, however it never took off as an industry standard for a variety of reasons; it was expensive to implement and therefore only available for high end servers, the standard was married to the x86 architecture on the host side and the Intel i860/960 architecture on the I/O controller side but the company was primarily developing that processor line as an embedded controller by this time and did not release new versions with improved I/O capabilities and in the end dropped the line altogether in favour of their x86 portfolio. On top of that the IOSIG organisation was expensive to join an did not publish open specifications which made them see hostile to small developers and open source projects, IOSIG was eventually disbanded in late 2000.

See also: I2OXPORT.SYS (OS/2 I2O driver)

Links

 * I2O Specification v1.5
 * UDI and I2O developers documentation on the Intel homepage.