th>Op/En</th>
<th>64-Bit Mode</th>
<th>Compat/Leg Mode</th>
<th>Description</th></tr>
<tr>
<td>FE /1</td>
<td>DEC <em>r/m8</em></td>
<td>M</td>
<td>Valid</td>
<td>Valid</td>
<td>Decrement <em>r/m8</em> by 1.</td></tr>
<tr>
<td>REX + FE /1</td>
<td>DEC <em>r/m8</em><sup>*</sup></td>
<td>M</td>
<td>Valid</td>
<td>N.E.</td>
<td>Decrement <em>r/m8</em> by 1.</td></tr>
<tr>
<td>FF /1</td>
<td>DEC <em>r/m16</em></td>
<td>M</td>
<td>Valid</td>
<td>Valid</td>
<td>Decrement <em>r/m16</em> by 1.</td></tr>
<tr>
<td>FF