System Organization Contents
Main Storage. Information Formats
Addressing I nformation Positioning Integral Boundaries.
Byte-Oriented-Operand Feature Central ,Processing Unit. General Registers Floating-Point Registers Control Registers I nput and Output Channels. Input/Output Interface. Input/Output Devices and Control Units.
System Console .
Logically, Systerri/370 consists of main storage, a
central processing unit (CPU), selector and multi­
plexer channels, and input/output devices, usually
attached to channels through control units. The
physical identity of these functions may vary be­
tween models. It is possible for systems to communi­
cate with each other by means of shared I/O de­
vices, a channel, or shared storage. The accompany­
ing illustration depicts the logical structure for a
single-CPU system and for a two-CPU mUltiprocess­
ing system.
Main
Storage
CPU
Channel Chennel
IBM System/370 Logical Structures
Channel
Main Storage
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Main storage provides the system with directly ad­
dressable fast-access storage of data. Both data and
programs must be loaded into main storage (from
input devices) before they can be processed.
Main storage may be either physically integrated
with a CPU or may be constructed as standalone
units. Additionally, main storage may be composed
of large-volume storage and a faster access buffer
storage, sometimes called a cache. Each CPU may
have an associated cache. The effects, except on
CPU
Channel
Main
Storage
CPU
Channel Channel System Organization 13
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