CENTRAL PROCESSOR
SIMULTANEOUS OPERATIONS
SIMULTANEOUS OPERATIONS
§ 110.
· 1 SPECIAL UNITS
Simultaneous operations are often dependent upon the inclusion of special units in a con-figuration. These units may be optional parts of a central processor, integral parts of peripheral controllers, or special multiplexing or time -sharing units.
· 11 Identity
Each unit which provides simultaneous operating facilities is listed. The full title, the model or serial number, and any abbreviated name used in the reports is stated . . 12 Description
A general description of a configuration's basic facilities is given, followed by the ef-fects of including each of the optional facilities. Each description emphasizes the value and use of each facility rather than a rigorous specification of the detailed times and interlocks.
There are five major kinds of technique which may be used to provide simultaneous operations:
Independent Operations
Multiple Data Paths arid Multiplexing Partial Overlapping
Restricted Operations Programmed Time -Sharing
· 13 Independent Operations
In general, independent operations are those in which the controllers concerned are using units which are not required by any other controller. A typical independent opera-tion is rewinding a magnetic tape. Other typical operaopera-tions are a controller searching on magnetic tape for a block with a specific key, data input or output using a buffer which is a separate store, and employing a buffer which is part of a store being used by other controllers but which has its own separate access device .
. 14 Multiple Data Paths and Multiplexing
Simultaneous data transfers, usually for input-output, are possible when each uses a separate data path. A special case exists when several paths share one cable but are multiplexed, or intermingled, in such a way that one cable is logically equivalent to several cables. Another common form of multiplexing is the time-sharing, or inter-mingling, of accesses to a store from many units. This is equivalent to multiplexing several data paths into a store .
. 15 Partial Overlapping
In many simple systems, input-output transfers cannot be overlapped with other opera-tions. In operations such as card reading, card punching, on-line printing, only part of an input-output cycle is covered by data transfers. There are usually periods at the start and end of each card cycle, or during paper movement, during which no access to storage is required. In these cases, some systems only prevent (interlock) the
© 1962 by Auerbach Corporation and BNA Incorporated 4/62
4:110.160 USERS' GUIDE
4/62
§ 110.
operation of the central processor during the transfer period, and permit computing during the other periods in input-output cycles .
. 16 Restricted Operations
In a few rare cases, an input-output operation may only partially restrict the operation of a central procesor. One example might be the use of a special register for input-output transfers that is also used for multiplication. Then input-input-output inhibits only multiplication .
. 17 Programmed Time -Sharing
Programmed time -sharing is possible in some systems, in which case a routine is used to arrange data transfers for input-output in small units and these transfers must be carefully timed. The penalty paid in central processor time devoted to this type of activity depends upon the speed and type of facilities available. In the order of prefer-red facilities, there may be automatic interruption, a "test busy" facility, or nothing.
In the last case, instructions must be carefully timed by the programmer. Programmed time-sharing simulates multiplexed access to storage .
• 2 CONFIGURATION CONDITIONS
In order to define the facilities in a comprehensive way, the different conditions that affect simultaneous operations are listed. The conditions are usually a set of possible combinations of optional units. The various cases are labeled with Roman numerals . . 3 CLASSES OF OPERATIONS
In order to define the simultaneous operating facilities in a comprehensive way, the various operations that can be performed are grouped into classes. Each class is labeled with a capital letter: A, B, C, . . .
. 4 RULES
For each condition listed in paragraph .2, a set of rules is given which defines the re-strictions upon the number of possible simultaneous operations at any instant. In these rules, the lower case letters a, b, c, d, e, ... represent the number of operations occurring at one time of classes A, B, C, D, E ... respectively.
Examples:
a
+
b+
c = at most 1means that not more than one operation out of those in classes A, Band C can be occurring at one time.
a = at most N
means that the number of operations of class A occurring at one time cannot be more than the number of operating units provided; e.g., the number of tape units.
ab = 0
means that if one or more operations of anyone class, A or B, are occurring, none can be occurring in the other class.
(a
+
b) c = 0means, first, that if any operation of class C is occurring, none of those in A or B can occur; and, second, that if any operations in either or both classes A and B are occurring, none of class C can occur.
Note that at anyone time, all the restrictions must be conSidered; thus a
+
b=
at most 1a
+
b+
c = at most 2/
,/
\ .... ,
SIMULTANEOUS OPERATIONS 4:110.500
§ 110.
mean that either one operation of class A, or one operation of class B, two operations of class C, or one operation of class A or B and one operation of class C, are possible at one time .
. 5 TABLE OF POSSIBLE SETS OF SIMULTANEOUS OPERATIONS
In some cases, the rules covering simultaneous operations are not straightforward; a tabular presentation, in these instances, may assist the explanation (see example below).
A table may be given for different conditions enumerated in 2.
The rows of the table correspond to the groups A, B, C, ... of operations. Each column corresponds to a possible mode of simultaneous operations.
A blank entry means that in that column, the operations in the group of that row are not possible.
An entry "1" means that one operation of that group is possible in the mode represented by its column.
An entry "N" means that the number of operations in that group is limited only by the number of operating units provided.
An entry "N-b" means that the number of operations in that group and group B together cannot be more than the number of operating units provided.
Example:
a
+
b a+
b+
cat most 1 at most 2 could be tabulated as:
CLASS POSSIBLE MODES OF SIMULTANEOUS OPERATION
A 1
B 1
C 1 1 2
The table enumerates several modes in each of which no further simultaneous operations are possible. The table implies that sub-modes of simultaneous operations are allowed:
e . g., one operation of type C.
© 1962 by Auerbach Corporation and BNA Incorporated 4/62
• STANDARD
4:120.100
E D P
• REPORTS
Users' Guide Instruction List INSTRUCTION LIST
§ 120.
A comprehensive list is given of the instruction repertoire of the computer system. The meanings given for the operations are abbreviated and use the notation of the manufac-turer. It is intended only to show the style and scope of the facilities .
. 1 ' INSTRUCTION
For each operation code is shown a symbol for each part of the instruction using the notation explained in 4:041.223. The mnemonic operation codes are those of the most common machine -oriented language .
• 2 OPERATION
The table is arranged by groups of operations, and the meaning of each operation is given in abbreviated form using abbreviations which are widely used and understood . . 3 ARITHMETIC
This group includes all fixed and floating point operations . .4 LOGIC
This group includes Boolean operations, comparisons, jumps, use of indicator bits, re-peat, tally and index control operations .
. 5 INPUT-OUTPUT
This group includes all operations concerned with input-output units except testing of status and other conditions which are covered in the Logic group .
. 6 AUXIUARY STORAGE
This group includes all operations concerned with auxiliary storage except testing of status and other conditions which are covered in the Logic group .
. 7 DATA TRANSFER
This group includes all operations concerned with movement of data within and between working storage and registers. It also includes editing and format control.
In some cases, extra headings may be used to improve the presentation.
In some cases, a list of unusual abbreviations is included.
© 1962 by Auerbach Corporation and BNA Incorporated 4/62
4:140.100
• STANDARD
•
E D P
REPORTS