I_O+instructions

=I / O Instructions / mechanism=

The S/370, 390, ESAME mainframe architecture has a rather elaborate IO paradigm.

With all three architectures, there are several reserved memory locations that are used by the I/O system.

There are also a number of data structures that the system requires to be prepared before an I/O operation is performed.

S/370 is very different than ESA/390 and ESAME (z/arch), the latter two being similar, with some subtle differences.

S/370

ESA/390

ESAME(z/arch)