1981 - System/370 XA (Extended Architecture)

• 1981 - System/370 XA (Extended Architecture)

  • 31bit addressing (2GB)

• Logical Partitioning

• 1990 System/390 ESA (Enterprise Systems Architecture)

  • Parallel Sysplex (up to 32 x 10-way MP's)

• 2000 - ^ zSeries

  • 64-bit addressing