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System/370 Extended Architecture
System/370 extended architecture is System/370 architecture with certain
exclusions and a set of functional extensions. The new facilities provided by
System/370 extended architecture as implemented in the 4381 Processor are the
following:
A 31-bit addressing capability that provides for addressing more than two
gigabytes (2G-bytes) of virtual and real storage
•
Dynamic channel subsystem architecture that provides additional channel
control functions that are designed to improve
1/0
performance
•
An expanded trace capability that provides for branch tracing, address space
tracing, and explicitly initiated tracing
•
Page protection, which can be used to prevent storing into selected virtual
storage pages (see Section 50)
•
An instruction (START INTERPRETIVE EXECUTION) to handle
interpretive instruction execution that provides a mechanism for implementing
virtual machine support
A sort microcode assist
The new capabilities provided in System/370 extended architecture are designed to
extend the functional capabilities of System/370 architecture while maintaining
compatibility between the two architectures for problem programs. The instruction
set for System/370 extended architecture includes all the problem state and
semiprivileged instructions defined for System/370 mode of operation (including
MOVE INVERSE).
The instruction set for System/370 extended architecture contains all the privileged
instructions defined for System/370 architecture except the following:
•
INSERT STORAGE KEY (ISK)
•
SET STORAGE KEY (SSK)
RESET REFERENCE BIT (RRB)
CLEAR CHANNEL (CLRCH)
CLEAR
I/
0 ( CLRIO)
•
HALT DEVICE (HDV)
HALT
1/0
(HIO)
RESUME I/O (RIO)
START
1/0
(SIO)
START
1/0
FAST RELEASE (SIOF)
Section 10: Technology and Architecture
23
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