Just last summer, IBM Corp. wowed the world with a supercomputer capable of performing one thousand trillion calculations per second, also known as a petaflop. Today, the Armonk-based computer giant is announcing a new machine that's up to 20 times faster.

Code-named Sequoia, the supercomputer has been ordered up by the U.S. Department of Energy's National Nuclear Security Administration, an agency that has long relied on IBM to provide the supercomputing muscle to safeguard the nation's nuclear stockpile.