Cray CRAY-1 - Vector Add Unit; Vector Shift Unit; Vector Logical Unit

This recursive characteristic of vector processing is applicable to any
vector operation, arithmetic or logical. The value initially placed in
element
0 of the operand/result register will depend on the operation
being performed.
For example, when using the floating point multiply
unit, element 0 of the operand/result register will usually be set to an
initial value of 1.0.
Vector add unit
The vector add unit performs 64-bit integer addition and subtraction for
a vector operation
and delivers the results to elements of a V register.
The unit implements instructions 154 through 157. The addition and sub-
traction are performed in a similar manner. However, for the subtraction
operations,
156 and 157, the Vk operand is complemented prior to addition
and during the addition a one is added into the low order bit position of
the
result.
No overflow is detected by the unit.
The functional unit time for the vector add unit is three clock periods.
Vector
shift unit
The vector shift unit shifts the entire 64-bit contents of a V register
element or the 128-bit value formed from two consecutive elements of a
V
register. Shift counts are obtained from an A register, Shifts are
end-off with zero
fill.
The vector shift unit implements instructions 150 through 153. Functional
unit time
is four clock periods.
Vector logical unit
The vector logical unit performs bit-by-bit manipulation of 64-bit
quantities for instructions 140 through 147. The unit also performs the
logical operations associated with the vector
mask instruction, 175.
Because the 175 instruction uses the same functional unit as instructions
140 through 147, it cannot be chained with these logical operations.
Functional unit time
is two clock periods.
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