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GIO-bus Architecture

The GIO bus is a family of synchronous, multiplexed address-data buses for connecting high-speed devices to main memory and CPU for entry-level Silicon Graphics systems. The GIO bus has three varieties: GIO32, GIO32-bis, and GIO64.

The members of the GIO-bus family are all similar; however, the GIO32 and GIO64 are not compatible. A GIO32 device does not work in a GIO64 slot, but a GIO32-bis device does fit in either a GIO32 or GIO32-bis option slot. It is possible to design a board that functions in systems with either a GIO32 or GIO32-bis bus.

The form factor and bus protocol depend on the specific platform in which the device is installed. GIO32 and GIO32-bis devices can be either single or double-wide (that is, taking one or both board slots), while GIO64 boards are the size of an EISA board. Slots in Indigo2 systems can accept either an EISA board or a GIO64 board. These two types of boards share common board dimensions but have different connectors for attaching to their respective buses.

The GIO Bus Specification contains more detailed information about the various types of GIO buses, from both an electrical and a mechanical point of view.



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