Cray CRAY-1 - Normalized Floating Point

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Normalized floating point
A non-zero floating point number in packed format is normalized if the
most significant bit of the coefficient is non-zero. This condition
implies
that the coefficient has been shifted to the left as far as
possible and therefore the floating point number has no leading zeros in
the
coefficient.
When a floating point number has been created by inserting an exponent
of 40060
8
into a word containing a 48-bit integer, the result should be
normalized before being used in a floating point operation. Normalization
is accomplished by adding the unnormalized floating point operand to zero.
Since So provides a 64-bit zero when used in the Sj field of an instruction,
a normalize of an operand in Sk can be performed using the following
instruction:
062iOk
Si cont~ins the normalized result.
Floating point range errors
Overflow of the floating point range is indicated by an exponent value of
60000
8
or greater in packed format. Underflow is indicated by an exponent
value
of 177778 or less in packed format. Detection of the overflow
condition will
initiate an interrupt if the floating point mode flag is
set in the mode register and monitor mode one is not in effect. The
floating point mode flag can be set or cleared by an object program.
Detection of
floating point range error conditions by the floating point
units is described in the following paragraphs.
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