Cray CRAY-1 - Arithmetic Operations; Integer Arithmetic; Integer Data Formats

ARITHMETIC OPERATIONS
Functional units in the CRAY-! either perform two's complement integer
arithmetic or perform
floating point arithmetic.
INTEGER ARITHMETIC
All integer arithmetic, whether 24 bits or 64 bits, is two's complement
and is so represented in the registers as illustrated in figure 3-2.
The address add unit and address multiply unit perform 24-bit arithmetic.
The scalar add unit and the vector add unit perform 64-bit arithmetic.
o
23
I I
I
SIGN
2
1
s COMPLEMENT INTEGER (24 BITS)
o
63
I I
I
SIGN
2
1
,
COMPLEMENT INTEGER (64 BITS)
Figure 3-2. Integer data formats
I Multiplication of two integer operands may be accomplished using the
floating point multiply
instruction. The floating point multiply unit
recognizes the conditions
where both operands have zero exponents as a
special case
and returns the upper 48 bits of the product of the
coefficients as the coefficient of the result and leaves the exponent
field zero.
Division of integers
would require that they first be converted to
floating point format
and then divided using the floating point units.
2240004
3-20
E-01