Cray CRAY-1 - Scalar Logical Unit; Population;Leading Zero Count Unit; Vector Functional Units

Scalar lo~ical unit
The scalar logical unit performs bit-by-bit manipulation of 64-bit
quantities obtained from S registers. It implements instructions 042
through 051, the mask and Boolean instructions. An operation requires
only one clock period.
Population/leading zero count
unit
This functional unit implements instructions 026 and 027. The 026
instruction, which counts the number of bits having a value of one in the
operand, executes in four clock periods.
The 027 instruction, which
counts the number of bits of zero preceding a one bit in the operand,
executes in
three clock periods. For either instruction, the 64-bit
operand is obtained from an S register and the 7-bit result is delivered
to
an A register.
When the Vector Population Instructions Option is installed, this unit
also recognizes an additional instruction, the 026ij1 instruction, which
returns a one-bit population count parity (even) of an S register1s
contents to an A register.
VECTOR FUNCTIONAL UNITS
Most vector functional units perform operations on operands obtained from
one or two V registers or from a V register and an S register. The
reciprocal unit, which requires only one operand, is an exception. Results
from a vector functional unit are delivered to a V register.
Successive operand pairs are transmitted to a functional unit each clock
period.
The corresponding result emerges from the functional unit n clock
periods
later where n is the functional unit time and is constant for a
given functional
unit. The vector length determines the number of operand
pairs to be processed by a functional unit.
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