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FPU: Difference between revisions
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:If the EM bit is set, all FPU and vector operations will cause a #UD so they can be '''EM'''ulated in software. Should be off to be actually able to use the FPU
'''CR0.ET''' (bit 4)
:This bit is used on the 386 to tell it how to communicate with the coprocessor, which is 0 for an 287, and 1 for a 387 or later. This bit is hardwired to 1 on 486+
'''CR0.NE''' (bit 5)
:When set, enables '''N'''ative '''E'''xception handling which will use the FPU exceptions. When cleared, an exception is sent via the interrupt controller. Should be on for 486+, but not on 386s because they lack that bit.
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