<a href="https:&#x2F;&#x2F;software.intel.com&#x2F;en-us&#x2F;blogs&#x2F;2012&#x2F;11&#x2F;17&#x2F;the-difference-between-rdrand-and-rdseed" rel="nofollow">https:&#x2F;&#x2F;software.intel.com&#x2F;en-us&#x2F;blogs&#x2F;2012&#x2F;11&#x2F;17&#x2F;the-differ...</a><p>rdseed directly gives you the output of a hardware RNG, limited by the rate that hardware RNG produces random bits.  rdrand gives you CSPRNG output seeded by rdseed.