Architects use the term interface width to refer to the number of parallel wires an
interface uses. Thus, one might hear an architect talk about an eight-bit interface or a
sixteen-bit interface. We will learn more about how interfaces use parallel wires in the
next chapter.
Serial Interface. The alternative to a parallel interface is one in which only one bit
of data can be transferred at any time; an interface that transfers one bit at a time is
classified as serial.
The chief advantage of a serial interface is fewer wires. Only two wires are needed
for serial data transmission — one to carry the signal and a second to serve as an
electrical ground against which voltage can be measured. The chief disadvantage of a
serial interface arises from increased delay: when sending multiple bits, serial hardware
must wait until one bit has been sent before sending another.