By TNL: GN22-0498
Multiprocessing
Contents
Shared Main Storage
Prefixing. . . .
CPU
Conditions Determining Response . . . . . . .
95
95
97
97
98
98
99
Conditions Precluding Interpretation of the
Status Bits
CPU Address Identification
The multiprocessing feature provides for the inter
connection of
order to enhance system availability and to share
data and resources. The multiprocessing feature in
cludes the following facilities:
Associated with these facilities are four extensions
to external interruption (external call, emergency
signal,
alert), which are described in the chapter
"Interruptions"; control-register positions for the
TOD-clock-sync-control bit and for the masks for
the four external-interruption conditions, which are
listed in "Control Registers" in the chapter "System
Control"; and the instructions SET
NAL
"System-Control Instructions."
When the
ing feature, certain additional functions are provided
as part of the system console. These functions per
tain to the following controls, which are described in
the chapter
trols, enable-system-clear key, load key, system
reset key, and TOD-clock key.
Channels in a multiprocessing system are associat
ed with a particular
conditions are directed to that
The shared-main-storage facility permits more than
one
locations. All
associated key in storage. All
main-storage location using the same absolute ad
dress.
Prefixing
When the multiprocessing feature is installed in a
ences by the
called "prefixing." All addresses subject to this pro
cessing are referred to as
addresses which are not subject to this processing,
and all addresses that have been processed, whether
or not they are changed, are referred to as
"absolute" addresses.
As a result of the processing to form the absolute
address, real addresses
the
address identified in the prefix register. All other real
addresses remain unchanged.
The real addresses
of the assigned storage locations that are implicitly
generated by the
addresses that can be specified by the program with
out the use of a base address or an index. Prefixing
provides the ability to reassign this block of real
locations for each
lute main storage, thus permitting more than one
with a minimum of interference,cespecially in the
processing of interruptions.
Because the prefixing mechanism interchanges
the real addresses, each
lute main storage, including the first
the assigned locations for another