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Abstract

A microprocessor includes one or more registers which are architecturally defined to be used for at least two data formats. In one embodiment, the registers are the floating point registers defined in the x86 architecture, and the data formats are the floating point data format and the multimedia data format. The registers actually implemented by the microprocessor for the floating point registers use an internal format for floating point data. Part of the internal format is a classification field which classifies the floating point data in the extended precision defined by the x86 microprocessor architecture. Additionally, a classification field encoding is reserved for multimedia data. As the microprocessor begins execution of each multimedia instruction, the classification information of the source operands is examined to determine if the data is either in the multimedia class, or in a floating point class in which the significand portion of the register is the same as the corresponding significand in extended precision. If so, the multimedia instruction executes normally. If not, the multimedia instruction is faulted. Similarly, as the microprocessor begins execution of each floating point instruction, the classification information of the source operands is examined. If the data is classified as multimedia, the floating point instruction is faulted. A microcode routine is used to reformat the data stored in at least the source registers of the faulting instruction into a format useable by the faulting instruction. Subsequently, the faulting instruction is re-executed.

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First Claim