On exhibit in the Museum are two Cray supercomputers. NSA has been a leader in computer development throughout its history. Some of the earliest supercomputers were designed and built specifically for the National Security Agency. The XMP-24 on display is the upgrade to the original XMP-22 that was the first supercomputer Cray ever delivered to a customer site. It was in operation from 1983 to 1993 and was arguably the most powerful computer in the world when it was delivered. The second generation Cray, the YMP, replaced the older version in 1993. In 1993 most personal computers held only 16 million bytes. The YMP used vector processing, a very powerful form of overlapping, parallel processing to conduct 2.67 billion operations per second. The YMP was decommissioned and went on display at the Museum in 2000.