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Chapter 10 - I/O System (Characteristics of I/O devices (Data-transfer…
Chapter 10 - I/O System
I/O Hardware
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Fiber channel (FC)
complex controller, usually separate circuit board (host-bus adapter, HBA) plugging into bus
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Performance
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Improving performance
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Reduce interrupts by using large transfers, smart controllers, polling
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Polling
For each byte of I/O
- Read busy bit from status register until 0
- Host sets read or write bit and if write copies data into data-out register
- Host sets command-ready bit
- Controller sets busy bit, executes transfer
- Controller clears busy bit, error bit, command-ready bit when transfer done
Interrupts
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Used for time-sensitive processing, frequent, must be fast
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