The first-generation metal–oxide–semiconductor (MOS) chips used p-channel field-effect transistors, known as p-channel MOSFETs (p-channel describes the configuration of the transistor). These ICs were used in calculators and in the first microprocessor, the Intel 4004. They were easy to produce but were slow and difficult to interface to the popular TTL digital logic ICs. An n-channel MOS integrated circuit could operate two or three times faster and was compatible with TTL. They were much more difficult to produce because of an increased sensitivity to contamination that required an ultra clean production line and meticulous process control. Motorola did not have an n-channel MOS production capability and had to develop one for the 6800 family.