International Business Machines Corp. (NYSE: IBM), the No. 2 computer maker, ranks first among supercomputer makers in the 2012 rankings compiled by U.S. and German experts.

IBM's Sequoia machine, part of its BlueGene/Q series, installed at the U.S. Department of Energy's Lawrence Livermore Laboratory in Livermore, Calif., has more than 1.5 million processors to perform more than 16 quadrillion calculations a second.

In second place, Fujitsu Ltd.'s (Pink: FJTSY) K unit, followed in third place by another IBM machine at Argonne National Laboratory in Lemont, Ill.

The Top500 rankings are published by German computing professor Hans Meuer and U.S. counterpart Jack Dongarra.

IBM shares closed at $198.78, down 15 cents, in Wednesday trading..