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In the Intel IA-32 software developer manual. It says that bit 8 & 9 of x87 FPU control word determines the precision of floating-point calculations. The default precision is double extended precision. After the instruction "FINIT" is executed, the precision is set to double-floating. The problem is that, after "FINIT" is executed, x87 FPU use only 64 bit of the 80-bit data registers to calculate. And the FPU can't accept(output) double-extended precision floating value from(to) memory. Is this right?

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不，这是不对的。当从内存加载/存储到内存时，FPU 会自动从 64 位转换为 80 位。

于 2013-12-22T11:04:18.500 回答