last three bits of fraction precision, can be obtained via conversions to G_floating, G arithmetic operations, then conversion back to D_floating.” (9, 2-6)The reordering of bits required for a D_floating load or store is identical to that of G_floating load and store instructions, therefore those instructions are used for loading or storing D_floating data. Except for 32 additional fractional bits of low significance, the memory form of a D_floating datum is identical to that of a F_floating datum. Within the fraction, bits of increasing significance are from 48 through 63, 32 through 47, 16 through 31, and 0 through 6. “The exponent conventions and approximate range of values is the same for D_floating as F_floating.” (9, 2-6)According to the Alpha Architecture Handbook hardware support is not provided by the Alpha 21164 for the following data types: Octaword (VAX data type) H_floating D_floating (except noted previously) Variable-Length Character String Trailing Numeric String Leading Separate Numeric String Packed Decimal String(9,2-12)In summation, the Alpha 21164 supports four integer data types, two IEEE floating-point data types, and three VAX floating point data types. The integer data types utilize the EXTRACT, MASK, and INSERT instructions. The floating-point data types use combinations of different LOAD and STORE instructions and in doing so, perform some bit reordering. In order to accommodate some of the floating point data types other data type instructions are used as in the VAX convention D_floating. ...
