Question

Why did Intel initially take the decision to implement its multimedia extensions without modifying the processor’s state architecture?

Answer 1

Answer)

As it had CR0.EM bit which was set and as this was a floating-point instruction hence there was a high chance of causing the FP emulation exception. The FP functionality supports the software emulation and as the MMX technology architecture state would have an overlapping with the FP architecture state hence it could lead to correcting the behavior for that of the MMX instruction when the CR0.EM would have been set. As the current FP emulator would not know the MMX instruction hence it would lead to emulation exception for the MMX instruction while the CR0.EM would be set but it would not have the right behavior. Hence intel took a decision for implementing the extension to the multimedia without having to modify the processor's state architecture.

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