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Input/Output_1 (I/O Requirements (An efficient means of transferring data…
Input/Output_1
I/O Requirements
An efficient means of transferring data directly
btwn I/O & memory for large data transfers
since programmed I/O is suitable only for
slow devices & indiv word transfers
Memory is a suitable medium for
direct block transfers, since data
has to be in memory for a
program to access it
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Buses that interconnect high-speed I/O
devices with the computer must support
high data transfer rates
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The I/O system must be capable of handling
devices operating at varying speeds with
varying amounts of delays
There must be means for addressing different
peripheral devices, such as keyboards & printers
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Basic Model
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Processing speed or program execution
is determined primarily by the ability of
I/O operations to stay ahead of processor
Usefulness dep on I/O
-may be many I/O devices all
trying to do I/O, sometimes
at the same time
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I/O interfaces
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It is not practical to connect the I/O devices
directly to the CPU without some sort of
interface module unique to each device
Advanced I/O techniques
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Direct Memory Access Controllers:
-Method for transferring data
btwn main memory & a device
that bypasses the CPU
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