This has been going on for a looooong time. Old time intel 486 &quot;SX&quot; chips without math co-processors (floating point unit really) were originally 486 &quot;DX&quot; with either the co-processor disabled or which failed QA. At some point, they made actual SX without FPU built-in.<p>The &quot;stand alone&quot; math co-processor you could add to an SX based system to gain h&#x2F;w floating point was actually a full blown 486 dx CPU with a different pin layout (one extra pin) so it couldn&#x27;t be used as CPU and could therefore be priced differently.