depend on this functionality in all Intel 64 or IA-32 processors.</p>
<p>In 64-bit mode, the instruction’s default operation size is 64 bits. The REX.R prefix must be used to access CR8. Use of REX.B permits access to additional registers (R8-R15). Use of the REX.W prefix or 66H prefix is ignored. Use of</p>
<p>the REX.R prefix to specify a register other than CR8 causes an invalid-opcode exception. See the summary chart at the beginning of this section for encoding data and limits.</p>
<p>If CR4.PCIDE = 