Cray CRAY-1 - Page 98

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--------------------------------------------------------------------

0020xk

Transmit

(Ak)

to

VL

1

1

1

1

1 1

1-----------------------------------------------------

_______________

1

This

instruction

enters

the vector length

(VL)

register

with a value

determined

by

the contents of

Ak.

The

low

order seven

bits

of

(Ak)

are entered

into

the

VL

register.

The

number

of

operations performed

is

determined

by

first

subtracting

one

from

the contents of

VL

and

then

adding

one

to the low-order

six

bits

of

the

result.

For

example,

if

(VL)

=

100

s

,

then

100-1

=

77

and

77+1

= 100.

However,

if

(VL)

= 0,

then

0-1

=

177

and

77+1

= 100. Thus, the

number

of vector operations

is

64

when

the content of

Ak

is

0 or

64

before executing the

0020

instruction.

Hold

issue conditions

034

-

037

in process

Exchange

in process

Ak

reserved

Execution time

Instruction

issue 1

CP

VL

register

ready 1

CP

Special cases

Maximum

vector length

is

64

(Ak) = 1

if

k = 0

(VL)

= 0

if

k

~

0

and

(Ak)

= 0

2240004

4-12

E

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