Section 3

The Instruction Repertory

In this Section are given detailed descriptions of the various functions in the Orion instruction repertory. Each description is given in a precise symbolic form and also verbally.  Exceptions and special cases are given and brief examples of the uses of some instructions.  When discussing some of the simpler groups of functions, a general introduction to the group is given, followed by a short description of the individual functions within that group.  The more complex instructions are described individually in detail.

It is assumed that the reader is familiar with the differences between the 2-address and 3-address types and with the modification and replacement facilities.  In these descriptions the X- and Y-addresses are the effective addresses at the time the instruction is obeyed, after all replacements and/or modifications have been done, including possibly pre-modification by one or more 116 and/or 117 instructions.

Timing of Orion Programs

Orion 1, like other machines of its generation, does not have fixed instruction times as do simple serial machines.  The following are some of the more important factors which introduce variations into instruction times.

1)  Carries

Orion has a parallel adder with a carry detection circuit and any micro-program operation which refers to the result of an addition or subtraction may be subject to a delay whilst waiting for this carry to die down. This applies particularly to the carries generated in a modification and the carry produced as a result of arithmetic orders although in this latter case, due to the carry-speed circuits and the fact that the next instruction is read before the result is written away, the maximum delay is 8 microsecs.

2)  Address Checking

The address-checking circuits on Orion, for both lock-outs and reservations, operate in a synchronous serial manner.  Reading from the core store can take place without waiting for the address checking to be completed, but at the end of each instruction that jumps or performs a write there may be a delay for this checking to be completed.  The core store operates in 12 microsecs. and an address can be checked in 16 microsecs so that instructions which do 4 operations on three addresses, such as the two address 00 instruction, can operate in 48 microsecs although this depends on starting the instruction at the correct phasing with respect to the address checking.  If an address which is being checked for lock-outs agrees with one of the lock-out addresses in the most significant 7 bits of the address (this address having been left justified through n places when the store has 215-n words) then the lock-out checking will take an extra l6 microsecs even though the word may not be locked out.

3)  Hesitations

When a peripheral transfer is initiated the number of words or characters called for is added into the program timer although when reading magnetic tape or using modes 1 or 21 on paper tape there may be less actual hesitations.  When a program is running at the same time as a peripheral device the peripheral device control unit has priority over the central machine in use of the core store and whenever the peripheral uses a core store cycle the timer does not get augmented; this happens whether or not the computer required access to the store at that time.  The occurrence of hesitations prevents the computer from making effective use of the 12 microsec core store cycle, on the other hand if a hesitation occurs at the time a jump instruction is about to jump, the jump can actually take place quicker than it otherwise would.

The time taken to obey a section of program on Orion is not directly the sum of the times for the individual instructions since each instruction time is a function of the conditions at entry and so depends on the preceding instructions in the program.  None-the-less it is hoped that the figures given below are useful averages when due notice is taken of the effects described above.  While efforts have been made to ensure accuracy, the times required by instructions may, in the end, be different for technical reasons from those given here.

3.A  Instruction Times for Orion 1

This section gives the average time taken to obey instructions.  For those which involve an arithmetical process (this includes comparisons made for jumps and table searching etc.) the time may be faster or slower than that stated, depending on the carries involved, i.e. on the operands.  The timing for the floating-point instructions depends to a great extent on the operands.

3.A.1  Orion 1 Instruction Times   ( Times in micro seconds)

Replacement of an address takes 16 microseconds.

 

3-address

2-address

2-add unmodified

Group 0

80

80

64

(03 and 04)

64

80

64

 

 

 

 

Group 1

64

64

48

(13 and 14)

48

64

48

 

 

 

 

Group 2

As for Group 0

 

 

 

 

 

 

Group 3

 

 

 

30,31

208

208

192

32

240

240

224

33

272

288

272

34

80+F

80+F

64+F

where   where n is the number of significant bits in Y.

Group 4 (average times for 4 runs)

40

765

773

755

41

700

718

686

42

1725

1737

1728

43

588

598

571

44

620

626

608

45

621

631

610

Group 5

n is the number of places shifted.

50 to 53

n<24

64+4n

64+4n

48+4n

n24

64+4(n-24)

64+4(n-24)

48+4(n-24)

54 to 57

n<48

128+4n

140+4n

112+4n

n>48

128+4(n-48)

140+4(n-48)

112+4(n-48)

54 for n=48

129+192

140+192

112+192

55-57 for n=48

As for n>48

 

 

For 54 and 55 if x*<0 then partial justification takes 16 microseconds.

 

3-address

2-address

2-add unmodified

Group 6

 

 

 

 

Jump, No Jump

Jump, No Jump

Jump, No Jump

60 to 62

120, 80

 96, 64

 64, 32

63 and 64

112, 80

 96, 64

 64, 32

65

120, 64

 96, 64

 64, 32

66

120, 64

 96, 64

 72, 32

67

104, 80

 96, 64

 72, 32

Group 7

 

 

 

 

Jump, No Jump

Jump, No Jump

Jump, No Jump

70 to 73

 96, 64

 80, 48

 64, 32

74

 80, 64

 --, 48

 --, 32

75

 96, 48

 80, --

 64, --

76 and 77

 96, 48

 80, 48

 64, 32

Group 8

 

 

 

 

Jump, No Jump

Jump, No Jump

Jump, No Jump

80

128, 64

144, 80

128, 64

81

 80, 112

 96, 128

 80, 112

82

112, 80

128, 96

112, 80

83

 96, 96

120, 112

 96, 96

84

 96, 166

128, 192

 96, 166

85

176, 80

208, 112

176, 80

86

 64

 80

 64

87

 72

 96

 64

Group 9

 

 

 

90

 160

 170

 153

91

 176

 186

 169

92

 160

 168

 152

93

 134

 144

 120

94

 272

 287

 256

95

 400

 416

 397

Group 10

 

 

 

100

 560

 560

 52

101

1203

1251

1203

102

129+4n

129+4n

113+4n

     where n = no. of shifts to standardise

103

 98+4n

 98+4n

 82+4n

     n=m or m-24, m is no. of places shifted

104

400

400

384

Group 11

 

 

 

110 and 112

 96

 80

 64

111

 88

 80

 64

114

112

112

 96

115

 80

 92

 64

116

 28

 32

 28

117

 32

 32

 32

 Group 12

120
 Y 0, n = Y                   68+4n               76+4n         48+4n
 Y < 0, n = 3-Y

121
   0 Y 23,  n = Y
  24 Y 255, n = Y-24 64+4n              64+4n         48+4n
 -23 Y -1,  n = 3-Y
-255 Y -24, n = -21-Y

122                       80                    96             112

123                     144+24E         172+24E     176

where E=8-n for n0 and E=0 for n=0, n being the number of characters to be changed.

124                      96+4n               76+4n         48+4n

where n is the no. of places shifted.  If Y<0 add 12 microsecs

125                   224+4m

where m is the no. of shifts needed to standardise.

126                   113                      124            101

 Group 14

142                   112+20Y            128+20Y    112+20Y

143                     96+30n               96+34n       96+30n

     n is the number of words

144,145,146     112+20n               illegal            illegal


3.A.2  Orion 2 Instruction Times

Times in microseconds

Replacement of an address takes 2.5 microseconds.
Modification of an address takes 3.5 microseconds.
Modification of two addresses takes 4.5 microseconds.

*   An asterisk indicates a typical value.

                3-address and 2-address unmodified

Group 0

00, 01, 02, 05, 07             12
03                                  10
04                                   8.5
06                                  11

Group 1

10, 12, 15                      10
11                                 11
13                                  8.5
14                                  6.5
16                                  8.5
17                                 10.5

Group 2

20, 21, 22, 25, 27            10.5
23                                   9.5
24                                   8.5
26                                 10

Add 1 microsecond for an odd pseudo-register.

Group 3

30                                 41.5
31                                 38
32                                 42
33                                 50
34                                 40.5

Group 4

40                               152
41                               150
42                               294
43                               150
44                               153
45                               153

Group 5

L = left shift, R = right shift, where L and R are directions of shift performed by the computer.

n = shift number

[x] = integral part of x.

Add 1 microsecond if shift number is negative.

d(x) = 1, x 0;      d(x) = 0, x = 0.

50, 51 L              11 + n

50, 51 R              11 +     + (n-1)mod 2 + d(n)

52,53 L               11 + 2  +     + n mod 2

52, 53 R              11 +    +    + n mod 2

54, 55 L            19.5 + 2n

54,55 R             19.5 +  + 2((n-1)mod 2) + 2 d(n)

56, 57 L              18.5 + 4  + 2   + 2(n mod 2)

56, 57 R              18.5 + 2  +    + 2(n mod 2)

  Add 1.6 microseconds for a partial justification.

                      3-address          2-address unmodified

Group 6

60 to 65              10.5                    8.5
66, 67               10.5                    8.5

         Add 1 microsecond for an odd pseudo-register.

 

                      3-address          2-address unmodified

Group 7

70 to 75                8.5                    6
76, 77                 10.5                    6

 

                      3-address or 2-address unmodified

Group 8

80 to 83

11

84 Successful jump     )
85 Unsuccessful jump )

10.5 + 2.8 ((n+1)mod 8)

84 Unsuccessful jump )
85 Successful jump     )

30

86

7.0

87

7.5

 

Group 9

90, 91

24 + n + 1.6m

92

25 + n + 1.6m

93

16.5 + 1.6m

94*

54

95*

160

97

26 + n + 1.6m


n is the difference in exponents
m is the number of places of shifting needed for restandardisation
For 90, 91, 92, 93, and 97, add 1 microsecond if ye > xe.

Group 10

100*

  130

101*

  140

102*

  380

103*

  288

104*

  50

 

  3-address     2-address unmodified
Group 11
110  15  12
111, 112   14  10.5
114  15 15
115 12.5  12.5
116, 117 8.5 8.5
  Add 1 microsecond for an odd pseudo-register.

 

Group 12

 120   

 13.5 + 1.6n + m
 
n is the number of places shifted.

 13.5 + 1.6n + m
 m is the number of 1ís.

 
 121

 
 11 + +   + n mod 2

  n is the number of places shifted.

 
Same as 3-address.

 122   

 10.5 + m
 m is the number of characters shifted.

 13 + m

 123   

 21 + 2m (m0); 14.5 (m=0)
 m is the number of characters unchanged.

 23.5+2m (m0);
 16.5 (m=0)

 124   

 

 

 16 + 2.6n
 
Add 1 microsecond if a 1 is found.
 Add 1 microsecond of Y < 0
 n is the number of places shifted.

 12.5 + 2.6n

 

 

 125   

 

 217 + 70m
 
m is the number of places shifting
 needed for restandardisation.

 

 217 + 70m

 

* 126*   

    220   

 220

Group 14

142 pair 36.5 + 6.1n  36.5 + 6.1n
143  17.5 + 2.9n 17.5 + 2.9n
144, 145  13.5 + 4.9n illegal
146
 
16 + 7.5n
 
illegal