To pop the register stack, the processor marks the ST(0) register empty and increments the stack pointer (TOP) by 1.</p>
<p>This instruction’s operation is the same in non-64-bit modes and 64-bit mode.</p>
<h2>Operation</h2>
<pre>CASE (relation of operands) OF
    ST(0) &gt; SRC:
                         C3, C2, C0 ← 000;
    ST(0) &lt; SRC:
                         C3, C2, C0 ← 001;
    ST(0) = SRC:
                         C3, C2, C0 ← 100;
    Unordered:
                         C3, C2, C0 ← 11