Amdahl

Amdahl refers to two related uses in computing: Amdahl's Law, a principle of parallel computing, and Amdahl Corporation, the hardware company founded by Gene M. Amdahl to produce mainframe-class systems.

Amdahl's Law, formulated by Gene M. Amdahl in 1967, states that the theoretical speedup of a program using multiple processors is limited by the portion of the program that must be executed serially. If f is the fraction of execution time that is serial and N is the number of processors, the maximum speedup S(N) is S(N) = 1 / (f + (1 − f)/N). As N grows large, S(N) approaches 1/f. The law implies diminishing returns from parallelization when a significant serial component exists, and it assumes a fixed problem size and ignores parallel overhead such as communication and synchronization.

Amdahl Corporation, founded by Gene M. Amdahl in the early 1970s, produced high-end mainframe-class computers intended to compete with IBM System/360/370-era systems. Based in California, it offered its own line of mainframes and complementary software and peripherals, including the Amdahl 470 family. The firm played a role in the competitive landscape of enterprise computing during the 1980s and 1990s. In 1997 Fujitsu acquired Amdahl Corporation, and the brand was gradually integrated into Fujitsu's mainframe offerings.