gtpc3m0o | Concepts and Structures |
A few observations on tightly coupled multiprocessing, loosely coupled
multiprocessing, and multiprogramming within the TPF architecture, are
instructive:
- In a loosely coupled complex in which all CPCs are uniprocessors, there is
no need for the tightly coupled multiprocessing system programming
constructs. In this case, each CPC is a single I-stream engine with a
private main storage where separate copies of programs are processed.
- In an environment of a single CPC that consists of an ESA configuration of
multiple I-stream engines, there is no need for an XLF, because all module
data is directed to a single CPC where it is managed in the TPF system by a
single I-stream engine.
- Loosely coupled is more accurately described as the synchronization of
multiple CPCs sharing a set of modules, where each CPC can be composed of
multiple I-stream engines. From the viewpoint of module
synchronization, each CPC is a single I-stream engine.
- A communication mechanism, called interprocessor communications (IPC),
coordinates activity among
CPCs in a single loosely coupled complex by using the Multi-Processor
Interconnect Facility (MPIF) a feature.
- A TPF system can be configured without loosely coupled
multiprocessing. However, tightly coupled multiprocessing constructs
are always in place.
- The basic component of performance in the TPF system, multiprogramming, is
basic to the design of the TPF system. This makes it possible for
several Entries to be in progress at any one time, thereby enhancing
performance.