1. The capacities of I/O devices are magnitude order larger than that of main memory and hence direct interfacing is impossible.
2. The response times of I/O devices are magnitude order slower than that of CPU and hence direct interfacing is impossible.
3. It is always better to off load the I/O processing to a secondary processor on the I/O controller board then to depend on the primary CPU for I/O processing.
4. The variety of I/O devices in the market requires that a separate I/O controller exist for each device.
What statement(s) best explain the requirement for an I/O controller?