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File Number S360-01
Form A22-6889-0
Systems Reference Library
IBM System/360 MDdel 75
Functional Characteristics
This manual presents the organization, characteristics, functions
and features unique to the IBM System/360 Model 75. Major
areas described are: system structure, generalized information
flow, standard and optional features, instruction timings, and the
system control panel.
Descriptions of specific input/output devices used with the
IBM System/360 Model 75 appear in separate publications. (See
IB"A1 System/360 Bibliography, Form A22-6822.)
This manual assumes that the reader has a knowledge of Sys-
tem/360 as defined in the IB"AI System/360 Principles of Opera-
tion, Form A22-6821 and the IB"A1 System/360 System Summary,
Form A22-6810.
Copies of this and other IBM publications can be obtained through IBM Branch Offices.
Address comments concerning the contents of this publication to:
IBM Corporation, Customer Manuals, Dept. B98, PO Box 390, Poughkeepsie, N. Y. 12602
Contents
System Description 5 System Control Panel. 13
2365 Processor Storage 5 System Reset 13
Two-Way Interleaving . 5 Store and Display . 13
Four-Way Interleaving 8 Initial Program Loading 13
2361 Core Storage 8 System Control Panel Controls 15
2075 Processing Unit .. 8 Operator Controls ...... . 15
Storage Control Unit 10 Operator Intervention Controls 18
Instruction Unit 10
General Registers 10
Execution Unit 10
Checking 10 Instruction Times 21
Channels 10 Timing Considerations 21
2860 Selector Channel . 10 Timing Assumptions 21
Channel-to-Channel Feature 11 Average Times 21
2870 Multiplexor Channel ... 11 Legend for System/360 Timing (Average Times) 26
2870 Priority ... 11 Fixed and Floating-Point Arithmetic, Logical and
Channel-to-Channel Adapter Connection to 2870 11 Branching Operations ... 26
System Control Panel . . .................... . 11 Execute Instruction 27
Interruption Times ............... . 11 Convert Instructions .. 27
External Interruption 11 Binary Shift Operations 27
Supervisor Call Interruption 11 Variable Field Length Instructions-Average Times 28
Program Interruption 12 Input/Output Operations . 29
Machine Check Interruption 12 Variable Field Length Instructions-Detailed Times 29
Input/Output Interruption . 12 Legend for System/360 Timing (Detail VFL Times) 30
System/ 360 Model 75
System Description
The IB~I System/360 ~10del 75 is part of a series of Interval Timer
compatible, high performance, data processing sys- Storage Protection
tems. The Model 75 provides the reliability, conven- Direct Control Feature
ience, and confidence demanded by large scale busi- Optional features for any System/360 Model 75
ness and scientific computation. include:
The Model 75 includes the advantages, characteris- 2361 Core Storage (Model 3 )
tics, and functional logic established for the System/ Channel-to-Channel Feature
360, as defined in the IBM System/360 Principles of 2870 Multiplexor Channel Attachment Feature
Operation, Form A22-6821. The high performance of A variety of control units and input/output devices
its logical structure is principally due to: arc available for use with the Model 75. Descriptions
1. Access to 8 bytes in parallel with a 750-nano- of specific input/ output devices appear in separate
second cycle time. publications. Configurators for the I/O devices and
2. Overlap of instruction fetch from storage with systems components are also available. (See IBM
execution of current instruction. System/360 Bibliography, Form A22-6822.)
3. Overlap of address arithmetic and initiation of
operand fetch from storage with execution of previous
instruction.
4. An addressing adder with three parallel inputs
2365 Processor Storage
for simultaneous addition of base address, index, and
displacement. One, two, or four units of 2365 Processor Storage
5. Parallel execution of floating-point arithmetic Model 3 provide main storage for the Model 75. Each
~10del 3 has a storage capacity of 262,144 bytes. Byte
operations (three-byte or seven-byte fractions).
6. Parallel execution of fixed point arithmetic. locations are consecutively numbered starting with
:Major components comprising a System/360 Model zero. An addressing" exception is recognized when any
75 are: an IB~1 2075 Processing Unit, IBM 2365 Pro- part of an operand is located beyond the maximum
cessor Storage, IB~1 2.361 Core Storage, IBM 2860 Se- available main storage capacity. Storage protection
lector Channels, and IB~I 2870 "Multiplexor Channel is a standard feature.
with input/output devices attached to the channels
through control units (Figure 1).
The three models of the Model 75 are termed H75, Two-Way Interleaving
175 and J75. They differ in the amount of 2365 pro- The 2365 Model 3 contains two independent storage
cessor storage required with a 2075 Processing Unit. sections, each of which can operate independently.
IBM PROCESSING
Each section has a 750-nanosecond storage cycle with
SYSTEM/360 UNIT
MODEL MODEL DESCRIPTION
access to eight bytes (double word) in parallel. Each
H75 2075H Requires one 2365 Processor Storage of the two sections in a 2365 Model 3 has 131,072
Model 3 (262,l44 bytes of storage) bytes of storage.
175 20751 Requires two 2365 Processor Storage
Model 3 (524,288 bytes of storage) The two sections are described as being two-way
J75 2075J Requires four 2365 Processor Storage interleaved. With interleaving, the two storage sec-
Model 3 (1,048,576 bytes of storage) tions in a 2365 operate independently in an over-
The H75 processor storage has two-way interleaving; lapped manner for improved sequential access. The
processor storage for the 175 and J75 has four-way two sections are organized and controlled so that they
interleaving. function logically as a Single storage unit that is 16
Outline configurations of the Model 75's, produced bytes wide. That is, the storage unit can effectively
by the various combinations of a 2365 Processor Stor- access 16 sequential information bytes starting at four
age and a 2075 Processing Unit, are shown in Figure 2. word integral boundaries (Figure 3). With two-way
The standard features for any System/360 Model interleaving, an effective sequential access rate of 400
75 include: nanoseconds per double word (eight bytes) is pos-
Universal Instruction Set sible.
System Description 5
IBM 2365 Processor Storoge IBM 2361 Core Storage
(8 microseconds)
(.75 Mi croseconds)
Modell: 1,048,516 bytes
Modell: 131,072 Bytes
Model 2: 2,097,152 bytes
Model 2: 262,144 Bytes
(Without interleaving:
2075 Processing Unit H75 has one one Model 1 or one to
175 has two four Model 2's)
System 2075 Processing Unit )75 has four (With interleaving:
Model Model two Modell's, or
two or four Model 2's)
H75 2075H
175 20751 To Model
)75 2075) 50,65,
or 75
IBM 2860 Selector Channel Up to Eight
Control
First Selector Channel Unitst
Channe I-to-Channe
Adopter t
Up to Eight
Control
Second Selector Channel Units t
Channe I-to-Channe I
Adapter t
Up to Eight
Controi
Third Selector Channel Units t
Channe I-to-Channe I
Adapter t Each selector channel addresses up to 256 I/O
devices, one at a time. Operation is in burst
mode with over lopped processing. The IBM
2860 Selector Channel has three models:
Modell - one channel } Max _ two units
Model 2 - two channels
Model 3 _ three channels Min - one unit (or 2870)
IBM 2870 Multiplexor Channel Up to Eight
Control
Units t
Addresses up to 192 I/O Devi ces
Up to Eight
Control
Units T
-Up to Eight
Control
Units r
Up to Eight
Control
Units +
Up to Eight
Control
Units t
Addresses up to 16 I/O Devices
NOTES: