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From: John R. <jr...@bi...> - 2011-11-08 16:50:04
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> [snip] to my > knowledge, there are no Intel processors that have hardware support for DFP. The x87 FPU (about 30 years old) and all x86 CPUs beginning with Pentium (1993) have FBLD and FBSTP which load or store signed 18-digit packed BCD integers to or from internal binary floating point [which is compatible with IEEE 754-1985: sign, 15-bit biased exponent, 64-bit significand with implied leading '1'; various control and status bits.] In addition, all x86 CPUs before x86_64 have AAA, AAD, AAM, AAS (Ascii Adjust after Addition/Division/Multiplication/Subtraction) which facilitate BCD arithmetic. These are supported by CPU flag bit AF (AsciiFlag) which is the CarryOut from bit 3 [the bit with positional value (1<<3).] Although this is not directly the scheme specified by IEEE 754-2008, such hardware does support decimal floating point arithmetic several times faster than is possible in a software-only implementation. -- |