X with <em>m64</em>. If equal, set ZF and load ECX:EBX into<em> m64</em>. Else, clear ZF and load <em>m64</em> into EDX:EAX.</td></tr>
<tr>
<td>
<p>REX.W + 0F C7 /<em>1 m128</em></p>
<p>CMPXCHG16B <em>m128</em></p></td>
<td>M</td>
<td>Valid</td>
<td>N.E.</td>
<td>Compare RDX:RAX with <em>m128</em>. If equal, set ZF and load RCX:RBX into<em> m128</em>. Else, clear ZF and load <em>m128</em> into RDX:RAX.</td></tr></table>
<p><strong>NOTES: *See IA-32 Architecture Compatibility section below.</strong></p>
<h3>