Power ISA™ Version 2.03 - Power.org

Version 2.03
Denormalized numbers of both positive and negative
sign are represented by a biased exponent value e of 0
and a fraction f, which is nonzero. For these numbers,
the hidden bit is defined by the IEEE 754 standard to
be 0. This number type is not directly supported in
hardware. Instead, either a software interrupt handler is
invoked, or a default value is defined.
Not-a-Numbers (NaNs) are represented by a maximum
exponent field value (255 for single-precision, 2047 for
double-precision) and a fraction f which is nonzero.
7.2.3 Exception Conditions
7.2.3.1 Denormalized Values on Input
Any denormalized value used as an operand may be
truncated by the implementation to a properly signed
zero value.
7.2.3.2 Embedded Floating-Point Overflow
and Underflow
Defining pmax to be the most positive normalized value
(farthest from zero), pmin the smallest positive normalized
value (closest to zero), nmax the most negative
normalized value (farthest from zero) and nmin the
smallest normalized negative value (closest to zero),
an overflow is said to have occurred if the numerically
correct result (r) of an instruction is such that r>pmax or
r