Reliability test procedures: LSI circuits: Fault models make high-volume testing practical

The testing of large-scale-integrated circuits is a major factor in the cost of producing such digital devices as memory chips and microprocessors. Manufacturers could test earlier small- and medium-scale-integrated devices cheaply and exhaustively ― testing every possible state that the circuits could take up ― but they cannot do the same with LSI and very large-scale-integrated devices, because of the awesome number of states. For example, a 4096-bit random-access memory can have a total number of states, or combinations, of 2 raised to the 4096th power. With current test equipment operating at 10 megahertz, it would take an astronomical amount of time to test for every memory combination.