Central Processing Unit Every CPU incorporates the commercial instruction
set, which includes the standard instruction set and
the decimal instructions (listed in Appendix C), and
the associated basic computing functions, including: • Byte-oriented operands • General registers • Control registers, with bit positions "for the
block-multiplexing control bit (if block multi­
plexing is provided), for the interrupt-key and
interval-timer masks, for channel masks associ­
ated with installed channels, for monitor
masks, for control of installed machine-check­
handling facilities, and for the IOEL control (if
an installed channel has the I/O-extended­
logout facility). • Storage protection • Interval timer • Time-of -day clock • Basic system console functions
Additionally, the following features are available:
Floating-Point Feature
Includes the floating-point instructions (listed in
Appendix C) and the floating-point registers.
Universal Instruction Set Includes the instructions of the commercial instruc­
tion set and the floating-point feature.
Extended-Precision Floating-Point Feature
Includes the extended-precision floating-point in­
structions (listed in Appendix C).
External-Signal Feature
Includes the extension to external interruptions for
external signals, the control-register position for the
external-signal mask, and the means to accept exter- , nal signals.
Direct-Control Feature
Includes the external-signal feature and the instruc­
tions READ DIRECT and WRITE DIRECT.
CPU-Timer and Clock-Comparator Feature
Includes the clock comparator, the CPU timer, the
associated extensions to external interruption,
control-register positions for the clock-comparator
and CPU-timer masks, and these instructions: SET Appendix A. System/370 Features CLOCK COMPARATOR, STORE CLOCK COM­ PARATOR, SET CPU TIMER, and STORE CPU TIMER.
Translation Feature
Includes the following facilities: • Dynamic Address Translation (DAT). The
DAT facility includes the translation mecha­
nism, with the associated control-register posi­
tions and program-interruption codes, and ref­
erence and change recording. • Program-Event Recording (PER). The PER
facility includes the associated control-register
positions and extensions to the program­
interruption code. • Extended-Control (EC) Mode. • SSM Suppression. This facility includes the
control-register position for the SSM­ suppression-control bit and the program­
interruption code for special operation. • Store Status and Program Reset.
As part of these facilities, the following instruc­
tions are provided: LOAD REAL ADDRESS, PURGE TLB, RESET REFERENCE BIT, STORE THEN AND SYSTEM MASK, and STORE THEN OR SYSTEM MASK. Multiprocessing Feature
Includes the following facilities, which permit the
formation of a two-CPU multiprocessing system: • Shared Main Storage. • Prefixing. • CPU Signaling and Response. • TOD Clock Synchronization.
These facilities include four extensions to external
interruption (external call, emergency signal, TOD clock sync check, and malfunction alert), control­
register positions for the TOD-clock-sync control bit
and for the masks for the four external-interruption
conditions, and the instructions SET PREFIX, SIG­ NAL PROCESSOR, STORE CPU ADDRESS, and STORE PREFIX.
Conditional-Swapping Feature
Includes the instructions COMPARE AND SW AP
and COMPARE DOUBLE AND SWAP. PSW-Key-Handling Feature
Includes the instructions SET PSW KEY FROM ADDRESS and INSERT PSW KEY.
Appendix A. System/370 Features 249

Page of GA22-7000-4 Revised September 1, 1975
By TNL: GN22-0498 1/0
1 Channels
Every system includes at least one byte-multiplexer, block';'multiplexer, or selector channel, with these
possible additional features:
Command Retry
Fast Release
Limited Channel Logout (LCL) I/O Extended Logout (JOEL)
Channel Indirect Data Addressing (CIDA)
Clear I/O AvaUability of CPU Features on System/370 Models
System/370 Model CPU Feature 115 125 135 145 Commercial instruction set (includes standard Std Std Std Std instruc:tion set and decimal feature) Floating-point feature Opt B Opt B Extended-precision floating-point feature Opt Opt Direct·control feature Opt
2 Opt
2 Opt Opt Translation feature Std Std Std Std CPU-timer and clock-comparator feature Std Std Opt Opt Conditional-swapping feature Std Std Opt Opt PSW-kt3y-handl i ng featu re Opt Multiprocessing feature Explanation: Std Standard Opt = Optional = Not available BQxed features are offered as a single package.
1 Includes the MONITOR CALL instruction and associated control-register positions only when the translation feature is installed. 2 Only the external-signal feature portion is offered.
3 These combined four features are available for field installation only on purchased models. 250 System/370 Principles of Operation
155 Std Std Opt Opt B 158 165 168 Std Std
1 Std Std Std Std Opt Std Std Opt Std Std Std B Std Std Std Std Std Std Std Opt Opt