Appendix B
IEEE Floating-Point Conformance
A subset of IEEE Standard for Binary
The order of presentation parallels the order of the IEEE specification.
B.1 Alpha Choices for IEEE Options
Alpha supports IEEE single, double, and optionally (in software) extended double formats. There is no hardware support for the optional extended double format.
Alpha hardware supports normal and chopped IEEE rounding modes. IEEE plus infinity and minus infinity rounding modes can be implemented in hardware or software.
Alpha hardware does not support optional IEEE software trap enable/disable modes. See the following discussion about software support.
Alpha hardware supports add, subtract, multiply, divide, convert between floating formats, convert between floating and integer formats, compare, and square root. Software routines sup- port remainder, round to integer in
In the Alpha architecture, copying without change of format is not considered an operation. (LDx, CPYSx, and STx do not check for
Optional operations for differing formats are not provided.
The Alpha choice is that the accuracy provided by conversions between decimal strings and binary