z/Architecture, initially and briefly called
ESA Modal Extensions (
ESAME), is
IBM's
64-bit computing architecture for IBM
mainframe computers. IBM introduced its first z/Architecture-based system, the
zSeries Model 900, in late 2000. Later z/Architecture systems include the IBM z800, z990, z890,
System z9,
System z10,
zEnterprise 196, and
zEnterprise 114. z/Architecture retains
backward compatibility with previous 32-bit-data/31-bit-addressing architecture
ESA/390 and its predecessors all the way back to the 32-bit-data/24-bit-addressing
System/360.