<story><title>How many x86 instructions are there? (2016)</title><url>https://fgiesen.wordpress.com/2016/08/25/how-many-x86-instructions-are-there/</url></story><parent_chain></parent_chain><comment><author>gbrown_</author><text>How about undocumented instructions? Sandsifter[1] is an interesting project and the video from BlackHat[2] is a good watch. There&amp;#x27;s also a previous discussion of it on HN[3].&lt;p&gt;[1] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;github.com&amp;#x2F;Battelle&amp;#x2F;sandsifter&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;github.com&amp;#x2F;Battelle&amp;#x2F;sandsifter&lt;/a&gt;&lt;p&gt;[2] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=KrksBdWcZgQ&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.youtube.com&amp;#x2F;watch?v=KrksBdWcZgQ&lt;/a&gt;&lt;p&gt;[3] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;news.ycombinator.com&amp;#x2F;item?id=18179212&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;news.ycombinator.com&amp;#x2F;item?id=18179212&lt;/a&gt;</text></comment>
<story><title>How many x86 instructions are there? (2016)</title><url>https://fgiesen.wordpress.com/2016/08/25/how-many-x86-instructions-are-there/</url></story><parent_chain></parent_chain><comment><author>johnklos</author><text>More than 1,500! Holy cow!&lt;p&gt;While having instructions for everything that are slow in early models but can be significantly improved in silicon over time is one way to look at CISC, I genuinely wonder how much silicon is spent on instructions that are so rarely used they&amp;#x27;d be better in software.&lt;p&gt;Or to ask another way: how many instructions are in billions of x86 cores that rarely if ever get used? Hmmm...</text></comment>