I/O Interfaces; Ibus Interface - Silicon Graphics POWER CHALLENGE User Manual

I/O Interfaces

The main Challenge I/O subsystem consists of one or more IO4 boards,
which plug directly into the Ebus and use optional mezzanine cards.
Mezzanine cards are daughter boards that plug into IO4 boards to allow
expansion and customizing. See Appendix D for additional information on
mezzanine boards.
Controllers for I/O devices connect to the 64-bit-wide Ibus. The Ibus
connects to the Ebus through the IA and ID processors. These devices
manage transfers between the 1.2 GB per second Ebus and the 320 MB per
second Ibus. I/O resources connect to the 320 MB per second Ibus. Up to two
optional mezzanine cards plug into the Ibus on each IO4 board.
The IO4 is the fundamental component of the I/O subsystem. It contains all
of the I/O controllers needed to implement a basic Challenge system:
• an Ethernet controller
• two fast and wide 16-bit SCSI-2 controllers
• a VME interface port (using the VCAM or GCAM)
• four serial ports
• a parallel port
In addition, the IO4 board contains the logic for a flat cable interface (FCI),
which is used to connect to the VMEbus and optional visualization console.
The IO4 board also has connections for mezzanine cards, which are used to
provide expansion I/O controllers.

Ibus Interface

The IA and ID application-specific integrated circuits (ASICs) act as bus
adapters that connect the Ibus to the much faster Ebus. In addition to making
the necessary conversions back and forth between the two buses, the IA and
ID ASICs perform virtual address mapping for scatter/gather direct
memory access (DMA) operations and maintain cache coherency between
the Ebus and the I/O subsystem.
I/O Interfaces
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