The K computer – named for the Japanese word/numeral "kei" (京), meaning 10 quadrillion (1016)[4][Note 1] – was a supercomputer manufactured by Fujitsu, installed at the Riken Advanced Institute for Computational Science campus in Kobe, Hyōgo Prefecture, Japan.

The previous record holder was the Chinese National University of Defense Technology's Tianhe-1A, which performed at 2.507 petaflops.

[5] The TOP500 list is revised semiannually, and the rankings change frequently, indicating the speed at which computing power is increasing.

[17] The K computer comprised 88,128 2.0 GHz eight-core SPARC64 VIIIfx processors contained in 864 cabinets, for a total of 705,024 cores,[1][18] manufactured by Fujitsu with 45 nm CMOS technology.

The computer's water cooling system was designed to minimize failure rate and power consumption.

[20][24] Although the K computer reported the highest total power consumption (9.89 MW – the equivalent of almost 10,000 suburban homes) on the June 2011 TOP500 list, it is relatively efficient, achieving 824.6 GFlop/kW.

However, K's power efficiency still fell far short of the 2097.2 GFlops/kWatt supercomputer record set by IBM's NNSA/SC Blue Gene/Q Prototype 2.