Cromemco ZPU Z-80 Central Processing Unit Instruction Manual. Black and White Xerox copy. 21 pages of text and 2 page copy of large Schematic Rev. 5 Board Rev. E ZPU-020-0019. Includes Introduction, Operating Instructions, Power-On Jump, Z-80A Clock Frequency Selection, Address Mirror Selection, Refresh Enable, Altair or Imsai Installation, The S-100 Bus, ZPU Parts List, Limited Warranty, ZPU Schematic.