I/O and Service Processor (IOSP)
P/390 I/O Subsystem
S/390 Operating System
Figure 2. System/390I/OhandledbyI/OandServiceProcessor(IOSP)DeviceManagers/Drivers
The IBM S/390 Integrated Server is a combination of a System/390 processor and
an I/O and Service Processor (IOSP).While the S/390 instructions execute
natively on a dedicated CMOS chip on the P/390, as shown in Figure2, the
execution of the S/390's I/O is handled by I/O and Service Processor (IOSP) device
managers, device drivers and S/390 channel emulation.The S/390 design in the
IBM S/390 Integrated Server is unique
when compared to other S/390 processors.
In this implementation, selected S/390 devices (tapes and printers) are either
channel-attached (via S/390 Parallel Channel adapter or S/390 Serial Channel
adapter) or emulated utilizing I/O and Service Processor (IOSP) devices in a
manner that is transparent to the S/390.DASD devices can be attached via the
S/390 Serial Channel Adapter or emulated using 18GB HDDs in a manner that is
transparent to the S/390 operating system or application.
While this mix creates an environment with many exciting options for I/O
attachment and support, some S/390 capabilities are not available with this
example, the I/O design for the IBM S/390 Integrated Server does
not support multiple paths to the same physical device.This is a capability that is
exploited in other S/390 systems.
Use of the IBM S/390 Integrated Server for your business requires workload
planning to achieve favorable results.
The performance section, AppendixA, “Performance” on page29, along with the
worksheet, Chapter6, “Planning Worksheet” on page15, and the planning
information, Chapter7, “Planning Guide” on page17, are designed to help you
determine if your planned S/390 workload for the IBM S/390 Integrated Server is
Copyright IBM Corp. 1998 7