Given that many systems have a single bus that can be controlled by only one bus master at a time (and thus the CPU cannot use the bus for other activities during I/O transfers), explain how a system...

Given that many systems have a single bus that can be controlled by only one bus master at a time (and thus the CPU cannot use the bus for other activities during I/O transfers), explain how a system that uses DMA for I/O can outperform one in which all I/O is done by the CPU.